Support for imaging material

ABSTRACT

A resin coated paper-based support for an imaging material comprises a multilayered base paper and a polyolefin resin sheet on at least the image forming side of the paper base. The thickness, fiber length, pulp composition, and freeness of the paper layers comprising the multilayered base paper base are controlled in order to obtain an imaging material with high gloss, stiffness, and curl resistance. The polyolefin resin sheet may comprise one or more layers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a support for an imaging material, morespecifically to a support whose surface on one side of a paper substratecomposed mainly of a natural pulp where an image-forming layer is to beformed is coated with a resin sheet, which support not only can providean imaging material and a print thereon having a high visual gloss andbeing free of non-uniformity in gloss, particularly silver halidephotographic paper and a print thereon (silver halide photographic paperprint will be sometimes abbreviated as “photographic print”hereinafter), but also is improved in the property of peeling from acooling roll used when the support is produced so that no non-uniformityin peeling occurs, and further, which support has excellent curlresistance and an excellent stiffness and can be stably produced at ahigh speed.

2. Explanation of Related Art

Generally, an imaging material is constituted of a support for theimaging material and an image-forming layer provided on the support. Forexample, a silver halide photographic material, an inkjet recordingmaterial, a thermal diffusion transfer type heat transfer recordreceiving material, a heat-sensitive recording material or aphotosensitive-thermosensitive recording material is produced by formingan image-forming layer such as a silver halide photograph constitutinglayer, an ink receiving layer, a thermal transfer type heat transferrecord receiving layer, a heat-sensitive color-forming layer or aphotosensitive-thermosensitive color-forming layer on a support for animaging material, respectively, and optionally forming an undercoatlayer, a protective layer, and the like. In particular, a silver halidephotograph constituting layer is constituted of a silver halidephotograph emulsion layer, a protective layer, an undercoat layer,either an intermediate layer or a color mixing prevention layer, eithera halation prevention layer or a filter layer and an ultravioletabsorbent layer, or a combination of some of these. For example, asimple silver halide photographic material is structured by forming asilver halide emulsion layer and its protective layer on a support for aphotographic material. Further, a multi-layered silver halide colorphotographic material is structured by consecutively forming silverhalide color photograph constituting layers such as an under coat layer,a blue-sensitive silver halide emulsion layer and an intermediate layer,a green-sensitive silver halide emulsion layer and an ultravioletabsorbent layer, and a speed-sensitive silver halide emulsion layer anda protective layer, and the like on a support for a photographicmaterial.

There is conventionally well known a resin-coated paper support in whichthe surface of a base paper for a support for an imaging material iscoated with a resin having film formability. Concerning a support for aphotographic material for use in a silver halide photographic material,for example, there is known a support for a photographic material inwhich a base paper is coated with a resin having film formability,preferably a polyolefin resin. There is also known a support for aphotographic material in which both surfaces of a base paper are coatedwith a polyolefin resin. Further, after the application of the rapidphotographic development treatment method of a silver halidephotographic material, a support for a photographic material in whichthe both surfaces of a base paper are coated with a polyethylene resinis mainly practically used as a photographic paper, and the resin layeron one side where an image-forming layer is formed generally contains atitanium dioxide pigment for imparting sharpness as required.

Further, there is known a thermal transfer record receiving elementhaving, as a support, a resin-coated paper of which the resin coatinghas a surface roughness of 7.5 microinches-AA or less, particularly, apolyethylene-resin-coated paper of which the base paper issurface-coated with a polyethylene resin. There is also known an inkjetrecording sheet having a resin-coated paper as a support.

However, a resin-coated paper type support for an imaging material,i.e., a support which is formed of a base paper, particularly a basepaper composed mainly of a natural pulp, and which is surface-coatedwith a resin layer on a surface side where an image-forming layer is tobe formed, still has several serious problems, and actually, nosatisfactory achievement has been obtained.

First, in a resin-coated paper for use as a support for an imagingmaterial, a base paper is coated with a resin having at least filmformability, particularly a resin layer containing a polyethylene-basedresin, on a surface side where an image-forming layer is to be formed (asurface on which an image-forming layer is to be formed will besometimes abbreviated as a front surface, a resin layer coating on thefront surface will be sometimes abbreviated as a front resin layer, aside opposite thereto will be sometimes abbreviated as a reverse side,and a resin layer formed on the reverse surface will be sometimesabbreviated as a reverse resin layer). The above resin-coated paper isobtained by a series of steps of casting onto a running base paper afilm of polyethylene resin composition extruded through a slit die of amelting extruder; pressing them in a nip of a pressing roll and acooling roll to bond them; cooling the resultant laminate; and thenpeeling it from the roll. In this case, for producing a resin-coatedpaper for an imaging material for glossy use, there is used a coolingroll which has a mirror surface, a gloss surface or a finely roughenedsurface and has an excellent smoothness. In this manner, the front resinlayer in a molten state is brought into contact with the cooling rollhaving an excellent smoothness under pressure. Therefore, the frontresin layer could be processed so as to have a surface having anexcellent smoothness, and an imaging material using the aboveresin-coated paper as a support and a print thereon could have avisually high gloss. However, concerning an imaging material using anactually produced resin-coated paper as a support and a print thereon,it has not been possible to obtain any product having a high-glossappearance. Concerning a photographic paper using a resin-coated paperin particular, it has not been possible to obtain a photographic paperand a print thereon having a sufficiently high-gloss appearance.

The present inventors have therefore made studies for factors of thehigh-gloss appearance of imaging materials and their prints. As aresult, the gloss appearance is affected by various factors such as aresin-coated paper as a support, an image-forming layer and animage-forming method such as development, while it has been found thatthe gloss appearance is also greatly affected by the factor of aresin-coated paper as a support. The present inventors have thereforemade studies on the factor of a resin-coated paper which affects theappearance of gloss. As a result, it has been found that the glossappearance not only depends upon the factor of a resin layer but alsodepends upon a variety of factors including factors of the kind andproperties of a base paper composed mainly of a natural pulp such as thekind of a natural pulp and a fiber length, conditions of a papermaterial slurry such as additives for paper, contained in a papermaterial slurry, paper-making conditions such as a paper-making speed, abulk density increasing press conditions and machine calenderconditions, post-treatment conditions such as size press and tub sizepress, and further, the surface roughness of a base paper. It has beenalso found that as the thickness of a front resin layer of aresin-coated paper decreases, the gloss appearance of an imagingmaterial using the above resin-coated paper as a support and a printthereon decreases, and that when the above thickness is 31 μm or less,the above gloss appearance greatly decreases. A photographic materialfor glossy use is required to give a print having a high glossappearance, and the problem is that a photographic material which givesa photographic print having a poor gloss appearance is absolutely notsuitable for glossy use and has no commercial value.

Second, a resin-coated paper for an imaging material for glossy use isrequired to have high smoothness. When a base paper is coated with amolten resin by extrusion, however, as the thickness of a front resinlayer increases, in particular, when the above thickness is 20 μm orgreater or as the speed of production of the resin-coated paperincreases, in particular, when the above speed is 200 m/mn or greater,the peeling of the resin-coated paper from a cooling roll is degraded,and a non-uniformity in the form of a lateral height difference in awidth direction, called “peel non-uniformity”, occurs on theresin-coated paper. When the above peel non-uniformity occurs, animaging material using the resin-coated paper as a support and a printthereon cause gloss non-uniformity. The problem is that the glossappearance further deteriorates and that the commercial value thereofextremely decreases.

Conventionally, there are some methods proposed for overcoming the aboveproblems and some other problems of a support of a resin-coated papertype for an imaging material. For example, there is known a method inwhich crater-shaped pores which are liable to occur in the front resinlayer surface of a photographic support of a resin-coated paper type areprevented or overcome by double layer extrusion coating method by meansof co-extrusion coating or consecutive extrusion coating, to provide aphotographic support which is free of surface defects and is excellentin smoothness. However, the above method is insufficient for overcomingthe above-explained problems, and in particular, it is absolutelyinsufficient for improving the gloss appearance of an imaging materialusing a resin-coated paper as a support and a print thereon.

On the other hand, for improving a resin-coated paper in smoothness,there are known methods using a specific pulp such as a pulp having aspecific fiber length distribution, a pulp having specific fiber length,width and thickness, a specific conifer pulp or a specific low-densitypulp, a base paper having a specific physical property value such as abase paper having a Beck smoothness equivalent to, or greater than, aspecific value or a base paper having a surface roughness equivalent to,or smaller than, a specific value. For the same purpose, there is knowna method of hot calendering of a base paper or there is known a specificpaper-making method such as paper-making with a paper machine having anupper dehydration mechanism, paper-making with a Fourdrinier two-layerpaper machine or the bulk density increasing press of a wet paper.However, these methods are still insufficient for overcoming the aboveproblems, and in particular, they are absolutely insufficient forimproving the gloss appearance of an image material using a resin-coatedpaper as a support and a print thereon.

Meanwhile, the most simplest method for improving the smoothness of aresin-coated paper for glossy use is, generally, to increase thethickness of the front resin layer. However, as the thickness of thefront resin layer is increased, particularly, when the above thicknessis greater than 31 μm, there is caused a problem that a resin-coatedpaper, an imaging material using the resin-coated paper as a support andits print curl toward an image-forming layer side and are muchtroublesome to handle, i.e., a problem that the curl resistance isdegraded.

Further, a resin-coated paper is improved in smoothness by using a basepaper having excellent smoothness as a base paper for the resin-coatedpaper. However, there is often involved a problem that an imagingmaterial using the above resin-coated paper as a support and its printhave a poor stiffness. When an imaging material, a photographic materialin particular, has a poor stiffness, there is sometimes caused a problemthat the developability, automatic developability in particular, isdegraded. Further, a print is manually taken up for its appreciation,and a “panorama” having a large width has a problem that it is difficultto appreciate when it has a poor stiffness. An imaging material and itsprint are therefore required to have a strong stiffness, while, as aresult of studies by the present inventors, it has been found that thestiffness of an imaging material and its print greatly depends upon thestrength of stiffness of a resin-coated paper as a support and that thestiffness of the resin-coated paper greatly depends upon the strength ofstiffness of a base paper. However, the problem of stiffness of a basepaper often has a contradicting relationship with the smoothness of thebase paper, and the following inconsistent problems have been found.When the smoothness is good, the stiffness is poor. When the stiffnessis sufficient, the smoothness is poor, and as a consequence, thestiffness of an imaging material using the resin-coated paper as asupport and its print is poor, or the gloss appearance of the print, aphotographic print in particular, is poor.

There are some methods conventionally proposed for overcoming the aboveproblems of a support for an imaging material of a resin-coated papertype. JP-A-61-132949 discloses a method for providing a photographicsupport of a resin-coated paper type having a high rigidity and a highgloss by a photographic base paper formed of a first coating filmcomposed mainly of a low-density polyethylene and a second coating layercomposed of a polymer having a high rigidity modulus. As a polymerhaving a higher rigidity modulus, the above publication discloseshigh-density polyethylene (HDPE), polypropylene (PP), polycarbonate(PC), linear low-density polyethylene (LLDPE), polyamides such as nylon11, nylon 6 and nylon 66, and polyesters such as polyethyleneterephthalate (PET) and polybutylene terephthalate (PBT). However, theuse of the above method is still insufficient for improving the glossappearance of an imaging material using a resin-coated paper as asupport and a print thereon, and there occurs a problem that the curlresistance is degraded. That is, the following problem occurs. When apolymer having a high density is used as a polymer in the second coatinglayer, and in particular, with an increase in the above density or withan increase in the content of the above polymer in the coating layer, aresin-coated paper, an imaging material using the resin-coated paper asa support and its print show poor curl resistance.

Further, JP-A-7-120868 discloses a method in which at least twowater-resistant-resin-coated layers are formed and a water-resistantresin of a layer farthest from a base paper has a higher density than awater-resistant resin of any other layer(s), and JP-A-7-168308 disclosesa method in which at least two water-resistant-resin-coated layers areformed and a resin having a specific flexural modulus is used as awater-resistant resin for an outer-most layer, for improving theadhesion between a base paper and the water-resistant resin layers andthe property of peeling from a cooling roll, to provide a support for aphotographic paper of a resin-coated paper type. However, the abovemethods are still insufficient for improving the gloss appearance of animaging material using a resin-coated paper as a support and of a printthereon. Further, there occurs another problem that the resin-coatedpaper and an imaging material using the resin-coated paper as a supportare degraded in curl resistance. That is, the following problem occurs.When a water-resistant resin having a high density is used as awater-resistant resin in a coating layer, and in particular, with anincrease in the above density or with an increase in the content of theabove water-resistant resin in the coating layer, a resin-coated paper,an imaging material using the resin-coated paper as a support and itsprint show poor curl resistance.

DISCLOSURE OF THE INVENTION

Under the circumstances, it is therefore an object of the presentinvention to provide a support for an imaging material, which support isformed of a paper substrate composed mainly of a natural pulp and aresin layer coated on the front surface of the paper substrate, whichcan give an imaging material and its print having a high glossappearance and being free of gloss non-uniformity, and which isexcellent in productivity and economic performance in that the supportis improved in its peeling from a cooling roll used for its productionso as not to cause any non-uniformity in gloss, that the curl resistancethereof is improved, that the support has strong stiffness and that thesupport can be stably produced at a high speed.

The present inventors have therefore made diligent studies to develop asupport for an imaging material which support has the above desirableproperties, and as a result, have found the following. Aresin-coated-paper-based support for an imaging material, in which aresin sheet on a side where an image is to be formed and a base paperhave a multi-layered structure each or a resin-coated-paper-basedsupport for an imaging material in which a base paper has amulti-layered structure of a layer structure having a specific thicknessand containing a broad-leaved tree pulp having a specific fiber lengthand a resin sheet on a side where an image is to be formed is apolyolefin resin sheet, can give an imaging material and a print havinga high gloss appearance and being free of gloss non-uniformity, isimproved in the property of peeling from a cooling roll so that no peelnon-uniformity takes place, and can be stably produced in a high speed.

Further, it has been found that a support in which a resin sheet on aside where an image is to be formed has a multi-layered structure, a toplayer thereof contains a specific amount of a polyethylene-based resinhaving a density equivalent to, or higher than, a specific value and hasa specific thickness, a bottom layer thereof contains apolyethylene-based resin having a density less than a specific value,the content of the polyethylene-based resin being the largest in thebottom layer, and a paper substrate is composed mainly of a natural pulphaving a specific fiber length, can give an imaging material and a printhaving a high gloss appearance, excellent curl resistance and a strongstiffness, and can be stably produced at a high speed.

The present invention has been made on the basis of the above findings.

That is, according to the present invention, there is provided aresin-coated-paper-based support for an imaging material which supportcomprises a base paper and a sheet of a resin having film formabilitycoated at least on a side of the base paper where an image is to beformed, characterized in that the resin sheet on the side where an imageis to be formed and the base paper have a multi-layered structure each(the above support for an imaging material will be sometimes referred toas “support I for an imaging material” hereinafter).

According to the present invention, further, there is provided aresin-coated-paper-based support for an imaging material which supportcomprises a base paper and a sheet of a resin having film formabilitycoated at least on a side where an image is to be formed, characterizedin that the base paper has a multi-layered structure, a paper layeradjacent to the polyolefin resin sheet on the side where an image is tobe formed has a thickness equivalent to 10 to 40% of a thickness of thebase paper as a whole and is composed of a broad-leaved tree craft pulpbeaten to an average fiber length of 0.3 to 0.5 mm, and that, of theother layers of the base paper, a layer composed of a pulp compositionwhich is beaten to an average fiber length of 0.5 to 0.8 mm and containsat least 80% by weight of a broad-leaved tree craft pulp has a totalthickness equivalent to, or greater than, 60% of the thickness of thebase paper as a whole (the above support for an imaging material will besometimes referred to as “support II for an imaging material”hereinafter).

Further, according to the present invention, there is provided a supportfor an image material, which is formed of a paper composed mainly of anatural pulp, as a substrate, and a multi-layered resin sheet coated ona surface of the paper substrate where an image-forming layer is to beformed, characterized in that an upper layer (surface layer) A in themulti-layered sheet contains at least 50% by weight of apolyethylene-based resin (a) having a density of at least 0.940 g/cm³and has a thickness equivalent to, or smaller than, 50% of a thicknessof the multi-layered resin sheet, that a lower layer (or each of lowerlayers present below the surface layer) B contains a largest amount of apolyethylene-based resin (b) having a density of less than 0.940 g/cm³among polyethylene-based resins in the layer(s) B, and that the papersubstrate is composed mainly of a natural pulp having an average fiberlength of 0.45 to 0.65 mm (the above support for an imaging materialwill be sometimes referred to as “support III for an imaging material”hereinafter).

In the present invention, the “average fiber length” of pulp refers to alength weighted mean fiber length (mm) obtained by measuring a beatenpulp according to JAPAN TAPPI Paper Pulp Testing Method No. 52-89,“Method of testing paper and pulp for fiber length”.

PREFERRED EMBODIMENTS OF THE INVENTION

In the support I for an imaging material, provided by the presentinvention, the base paper and the resin sheet on a side where an imageis to be formed (front side) have a multi-layered structure each. In thesupport II for an imaging material, the resin sheet on the front side isa polyolefin resin sheet, the base paper has a multi-layered structure,and the layer structure is specifically constituted.

In the support I for an imaging material, provided by the presentinvention, it is not clear why the mere formation of the base paper andthe resin sheet as multi-layered structures improves the glossappearance. However, it is assumed that the following statisticalproperties work. When each of the base paper and the resin sheet isincreased in thickness as a single layer, the fluctuation of thethickness increases with an increase in thickness, while the division ofa layer into layers relatively lessens an increase in the fluctuationdue to a phase deviation of the fluctuation and a difference infrequency. It is also assumed that a combination of the base paper andthe resin sheet produces an effect not only for the above reason butalso because the size of concave and convex shapes on a surface comesinto the acute region of human eyes.

In the support I for an imaging material (to be sometimes simplyreferred to as “support I” hereinafter) and the support II for animaging material (to be sometimes simply referred to as “support II”hereinafter) provided by the present invention, the multi-layered basepaper can be formed by any one of a method in which amulti-layer-structured head box is used, a method in which pulp slurriesfor upper layers are consecutively fed onto a pulp slurry for a lowerlayer in the step of dehydration on a wire and a method in which layersmade in the form of sheets with a Fourdrinier paper machine or acylinder paper machine are combined. In view of an interlayer bondingstrength, however, it is preferred to form the multi-layered base paperat an early stage of paper making.

In the support I of the present invention, a paper layer adjacent to thefront resin sheet has a thickness, preferably, of at least 10 μm, morepreferably at least 30 μm, particularly preferably at least 50 μm and iscomposed of a natural pulp beaten to an average fiber length of 0.3 to0.5 mm. In this case, a further favorable result can be produced. Thepulp which forms layer(s) other than the above layer adjacent to thefront resin sheet is preferably that which is beaten to an average fiberlength in the range of from 0.5 to 0.8 mm. When the fiber length of thepulp in any one of the layer adjacent to the front resin sheet and theother layer(s) is too small, the internal bonding strength of the basepaper may decrease or the stiffness thereof may decrease. When the pulpfiber length of the layer adjacent to the front resin sheet is too largeand equivalent to the length of the pulp fiber length of the otherlayer(s), the effect of the present invention is limitative. On theother hand, when the pulp fiber length of the layers as a whole is toolarge, the practical commercial value of the support I decreasesalthough the effect of the present invention is exhibited as comparedwith a case where the present invention is not practiced.

On the other hand, in the support II of the present invention, the paperlayer adjacent to the polyolefin resin sheet on the front side has athickness equivalent to 10 to 40%, preferably 20 to 30%, of thethickness of the base paper as a whole, and is composed of abroad-leaved tree craft pulp beaten to an average fiber length of 0.3 to0.5 mm. Further, of the other layers of the base sheet, the layercomposed of a pulp composition which is beaten to an average fiberlength of 0.5 to 0.8 mm and contains at least 80% by weight of abroad-leaved craft pulp is required to have a total thickness equivalentto, or greater than, 60% of the thickness of the base paper as a whole.

When the fiber length of the pulp in any one of the layer adjacent tothe front resin sheet and the other layer(s) is too small, the internalbonding strength of the base paper may decrease or the stiffness thereofmay decrease. When the pulp fiber length of the layer adjacent to thefront resin sheet is too large and equivalent to the length of the pulpfiber length of the other layer(s), the effect of the present inventionis limitative. On the other hand, when the pulp fiber length of thelayers as a whole is too large, no sufficient gloss appearance can beobtained. When the layer adjacent to the front resin sheet is composedof a conifer pulp, or when the other layer(s) is composed of a largecontent of a conifer pulp, the outcome is that the gloss appearance isimpaired. When the layer adjacent to the front resin sheet is composedof a broad-leaved sulfite pulp, or when the other layer(s) is composedof a large content of a broad-leaved sulfite pulp, the stiffness isinsufficient. When the thickness of the layer which is composed of adesired composition and adjacent to the front resin sheet is less than10% of the total thickness of the base paper as a whole, the glossappearance is insufficient, and when the above thickness exceeds 40%,the stiffness is insufficient. When the total thickness of the layercomposed of a pulp composition which is beaten to an average fiberlength of 0.5 to 0.8 mm and contains at least 80% by weight of abroad-leaved craft pulp is less than 60% of the total thickness of thebase paper as a whole, some kinds of pulp used for compensating anamount deficiency may cause an insufficient stiffness or an insufficientgloss appearance.

Preferably, the above layer composed of a pulp composition which isbeaten to an average fiber length of 0.5 to 0.8 mm and contains at least80% by weight of a broad-leaved craft pulp is a layer having a thicknessequivalent to, or greater than, 60% of a paper layer as a whole, whichpaper layer continues from the paper surface on the side opposite to theside where an image is to be formed. More preferably, the above paperlayer consists of two layers, a layer composed of a broad-leaved treecraft pulp beaten to an average fiber length of 0.3 to 0.5 mm and alayer composed of a pulp composition which is beaten to an average fiberlength of 0.5 to 0.8 mm and contains at least 80% by weight of abroad-leaved craft pulp. on the other hand, when the layer composed of apulp composition which is beaten to an average fiber length of 0.5 to0.8 mm and contains at least 80% by weight of a broad-leaved craft pulphas other layer in an intermediate position thereof, and if the “otherlayer” is composed of a conifer pulp, the conifer pulp isdisadvantageous for the gloss appearance. A broad-leaved tree sulfitepulp is also disadvantageous in view of stiffness. Similarly, when otherlayer is present between the layer composed of a broad-leaved tree craftpulp beaten to an average fiber length of 0.3 to 0.5 mm and the layercomposed of a pulp composition which is beaten to an average fiberlength of 0.5 to 0.8 mm and contains at least 80% by weight of abroad-leaved craft pulp, and if the “other layer” is composed of aconifer pulp, the conifer pulp is disadvantageous for the glossappearance. A broad-leaved tree sulfite pulp is also disadvantageous inview of stiffness.

In the supports I and II of the present invention, the pulp ispreferably beaten so as to have a freeness in the range of from 250 mlto 360 ml, more preferably beanten to have a freeness of from 280 ml to330 ml. When the freeness of the pulp is too low, the pulp may showinsufficient paper making suitability, or the base paper may have lowstiffness. When the freeness of the pulp is too high, the base papertends to have a poor formation. In the present invention, the “freeness”refers to a freeness (ml) found by measuring a beaten pulp according toTAPPI Standard Pulp testing method No. T227m-58 “Freeness of Pulp”.

In the supports I and II of the present invention, the pulp having afiber length and a freeness in desirable ranges can be can be obtainedby optimizing a balance between the cutting-based beating and thebeating in a viscous state. Specifically, the balance between thecutting-based beating and the beating in a viscous state can beoptimized by beating the pulp under a series of combined experimentalconditions with regard to beating conditions such as a ratio of thecutting-based beating and the beating in a viscous state, a beatingtime, a pulp concentration and a beating power and measuring a sampledpulp slurry for a pulp fiber length and a freeness of the pulp.

In the supports I and II of the present invention, the layer(s) of thebase paper other than the paper layer adjacent to the front resin sheetis generally composed of a natural pulp, while the natural pulp maycontain a synthetic fiber or a synthetic pulp so long as it does nothamper the performance of the base paper. The natural pulp is preferablyselected from wood pulps such as broad-leaved tree bleached kraft pulp,broad-leaved tree bleached sulfite pulp, conifer bleached kraft pulp,conifer bleached sulfite pulp and broad-leaved tree/conifer mixedbleached sulfite pulp. Further, various pulps including non-wood pulp,soda pulp, dissolving pulp and others such as reclaimed pulp (recycledpaper pulp) may be used. In the support I of the present invention, thelayer(s) adjacent to the front resin sheet is preferably composed of abroad-leaved tree sulfite pulp or a broad-leaved tree kraft pulp. In thesupport II of the present invention, the layer(s) adjacent to the frontresin sheet is essentially required to be composed of a broad-leavedtree kraft pulp.

In the supports I and II of the present invention, each layer of thebase paper may contain various additives which are added when papermaterial slurries are prepared. The additives include sizing agents suchas fatty acid metal salt, fatty acid, emulsified alkyl ketene dimer orepoxidized higher fatty acid amide disclosed in JP-B-62-7534, emulsifiedalkenyl- or alkylsuccinic acid anhydride and a rosin derivative, drypaper strength reinforcing agents such as anionic, cationic oramphoteric polyacrylamide, polyvinyl alcohol, cationic starch andplant-originated galactomannan, wet paper strength reinforcing agentssuch as a polyamine polyamide epichlorohyrin resin, fillers such asclay, kaolin, calcium carbonate and titanium oxide, fixing agents suchas aluminum chloride and water-soluble aluminum salt including aluminumsulfate, pH adjusting agents such as sodium hydroxide, sodium carbonateand sulfuric acid and others such as colorant pigments, colorant dyesand fluorescent brighteners disclosed in JP-A-63-20425 andJP-A-1-266537. The above additives are advantageously used incombination as required.

In the supports I and II of the present invention, the base paper may beimpregnated with a composition containing any one of a water-solublepolymer, hydrophilic colloid or latex, an antistatic agent and otheradditives such as a pigment and a pH adjusting agent, or the abovecomposition may be applied to the base paper, by size press, tub sizepress, etc., or with a blade, an air knife, etc. The water-solublepolymer or the hydrophilic colloid includes a starch-based polymer, apolyvinyl-alcohol-based polymer, a gelatin-based polymer, apolyacrylamide-based polymer and a cellulose-based polymer. The emulsionor the latex includes a petroleum resin emulsion, an emulsion or latexcomposed of at least ethylene and acrylic acid (or methacrylic acid)disclosed in JP-A-55-4027 and JP-A-1-18053, and an emulsion or latex ofa styrene-butadiene copolymer, a styrene-acrylate copolymer, a vinylacetate-acrylate copolymer, an ethylene-vinyl acetate copolymer, abutadiene-methyl methacrylate copolymer or a carboxy-modified product ofany one of these. The antistatic agent includes alkali metal salts suchas sodium chloride and potassium chloride, alkaline earth metal saltssuch as calcium chloride and barium chloride, colloidal metal oxidessuch as colloidal silica and organic antistatic agents such aspolystyrene sulfonate. The pigment includes clay, kaolin, calciumcarbonate, talc, barium sulfate and titanium oxide. The pH adjustingagent includes hydrochloric acid, phosphoric acid, citric acid andsodium hydroxide. The above colorant pigment, colorant dye andfluorescent brightener may be also used. The above additives areadvantageously used in combination as required.

In the supports I and II of the present invention, the base paper ismade such that the layer thickness non-uniformity index Rpy in apaper-making direction to be defined below is preferably 250 mV or less,more preferably 200 mV or less, particularly preferably 150 mV or less.The term “layer thickness non-uniformity index” refers to a valueobtained by allowing a sample to run between two spherical tracers,scanning the sample in the paper-making direction of the sample afterzero adjustment at a constant speed of 1.5 m/minute with a filmthickness measuring apparatus which measures a thickness fluctuation ofthe sample as an electric signal through an electronic micrometer, underconditions where the sensitivity range of the electronic micrometer is±15 μm/±3 V, to measure the sample for a thickness fluctuation in thepaper-making direction, subjecting obtained measurement signal values tofast Fourier transform with an FFT analyzer using a hanning window as atime window, determining a power spectrum (unit: mV²) based on anaddition mean of additions carried out 128 times, totalling power valuesin the frequency band of 2 Hz to 25 Hz, multiplying the total by ⅔ andraising the obtained product to ½ power.

For producing a base paper having a layer thickness non-uniformity indexRpy of 250 mV or less for the support I of the present invention,specifically, there is used at least 30% by weight, preferably at least50% by weight, of a broad-leaved tree pulp which is properly beaten. Forexample, as a complete pulp for constituting the base paper, there isused a broad-leaved tree kraft pulp which is beaten to a fiber lengthof, preferably, 0.8 mm or less, more preferably 0.6 mm or less. Thelayer adjacent to the front resin sheet has a thickness of, preferably,at least 10 μm, more preferably at least 30 μm, particularly preferablyat least 50 μm. And, for the above layer adjacent to the front resinsheet, further preferred is a pulp which is beaten to a fiber length of0.3 mm to 0.5 mm. The base paper is preferably produced by making paperfrom the slurry containing additive chemicals with a Fourdrinier papermachine according to a proper paper-making method such that a uniformformation can be obtained.

For producing a base paper having a layer thickness non-uniformity indexRpy of 250 mV or less for the support II of the present invention,specifically, there is used at least 80% by weight of a broad-leavedtree pulp which is properly beaten. For example, as a complete pulp forconstituting the base paper, there is used a broad-leaved tree kraftpulp which is beaten to a fiber length of 0.8 mm or less, preferably 0.6mm or less. For the layer which adjacent to the front resin sheet andhas a thickness equivalent to 10 to 40%, preferably 20 to 30%, of thethickness of the base paper, the pulp is beaten to a fiber length of 0.3mm to 0.5 mm. The base paper is preferably produced by making paper fromthe slurry containing additive chemicals with a Fourdrinier papermachine according to a proper paper-making method such that a uniformformation can be obtained.

The base paper for each of the supports I and II can be produced by acombination of proper paper-making techniques in which a Fourdrinierpaper machine having a proper upper dehydration mechanism, which machinecauses proper turbulence on a paper material slurry, is used,multi-stage wet press, preferably at least three-stage wet press, isapplied to a wet part, a smoothing roll is provided at the final stageof a press part, such that a uniform formation can be obtained, and theobtained paper is calendered with a machine calender, a super calenderor a hot calender to form a base paper having a layer thicknessnon-uniformity index of 250 mV or less.

In the supports I and II of the present invention, the central planeaverage roughness SRa of the front surface of the base paper measured ina paper-making direction with a stylus-applied three-dimensional surfaceroughness tester at a cut-off value of 0.8 mm (the central plane averageroughness on the front surface of a base paper in a paper-makingdirection at a cut-off value of 0.8 mm, measured with a stylus-appliedthree-dimensional surface roughness tester, will be sometimes simplyabbreviated as “central plane average roughness SRa” hereinafter) isadvantageously 1.50 μm or less, preferably 1.40 μm or less, morepreferably 1.45 μm or less, most preferably 1.25 μm or less. In thepresent specification, the central plane average roughness at a cut-offvalue of 0.8 mm, measured with a stylus-applied three-dimensionalsurface roughness tester, is defined by the expression 1.${SRa} = {\frac{1}{Sa}{\int_{0}^{WX}{\int_{0}^{WY}{{{f\left( {x,y} \right)}}\quad {x}\quad {y}}}}}$

wherein Wx is a length of a sample surface region in an X-axis direction(paper-making direction), Wy is a length of the sample surface region ina Y direction (direction at speed angles with the paper-makingdirection), and Sa is an area of sample surface region.

Specifically, a machine SE-3AK and a machine SPA-11 supplied by KosakaLaboratories (Japan) are used as a stylus-applied three-dimensionalsurface roughness tester and a three-dimensional roughness analyzer, andthe central plane average can be determined under conditions where thecut-off value is 0.8 mm, Wx=20 mm, Wy=8 mm and therefore, Sa=160 mm². Indata processing in the X-axis direction, sampling was carried out in 500points, and scanning in the Y-axis direction is carried out in at least17 lines.

The base paper having a central plane average roughness SRa of 1.50 μmor less, which is preferably used for the supports I and II of thepresent invention, can be specifically produced as follows. While a wetpaper is dried, the wet paper is subjected to multi-staged bulk densityincreasing press. Further, the produced base paper is calendered in atleast two lines by means of a machine calender, a super calender or ahot calender. For example, in the first line, the base paper is treatedwith a machine calender or a hot machine calender or both, and in thesecond line and thereafter, the base paper is treated with a machinecalender as required and treated with a hot soft calender as describedin JP-A-4-110938. Preferably, the base paper is impregnated with awater-soluble polymer, a hydrophilic colloid or a polymer latex, or anyone of these is applied to the base paper, in an amount of at least 1.0g/m², preferably at least 2.2 g/m² by size press, tub size press, bladecoating or air knife coating.

In the supports I and II of the present invention, the density of thebase paper, excluding an ash content, is preferably 0.80 g/cm³ to 1.15g/cm³, more preferably 0.85 g/cm³ to 1.05 g/cm³, while the above densityshall not be limited thereto. The thickness of the base paper is notspecially limited, while the basis weight of the base paper isadvantageously 40 g/m² to 250 g/m², preferably 70 g/m² to 220 g/m².

In the supports I and II for an imaging material, provided by thepresent invention, the surface (front surface) of the base paper wherean image-forming layer is to be formed is coated with a resin sheetcontaining a resin having film formability. The reverse surface of thebase paper is preferably coated with a resin sheet containing a resinhaving film formability.

When the resin having film formability in the front resin sheet and theresin having a film formability in the reverse resin sheet arethermoplastic resin(s), the support I and II are produced by a so-calledmelt-extrusion coating method in which resin composition(s) for thefront resin sheet and the reverse resin sheet is/are cast in the form ofa film onto a running base paper through a slit die with a melt extruderto coat the base paper. Generally, the support is produced by a seriesof steps in which a molten resin composition is extruded in the form ofa film onto a running base paper through a slit die with a melt extruderand cast to coat the base paper, the so-formed films and the base paperare bonded under pressure between a press roll and a cooling roll andthe resultant laminate is peeled from the cooling roll.

The present inventors have found that the effect of the presentinvention can be greatly remarkably exhibited owing to synergisticeffects produced by constituting the front resin sheet of the support Ias a multi-layered structure and constituting the base paper as amulti-layered structure. That is, the following has been found. Byconstituting the front resin sheet of the support I for an imagingmaterial in the present invention as a structure of two or more layers,an imaging material having the above support and its print can beremarkably improved in gloss appearance, the support is remarkablyimproved in the property of peeling from a cooling roll when produced,to prevent the occurrence of peel non-uniformity, and therefore thesupport for an imaging material can be stably produced at a high speed.

The support I for an imaging material, provided by the presentinvention, has a front resin sheet constituted of two or more layers,while the front resin layer constituted of two layers is preferred foreffectively accomplishing the object of the present invention.

In the support II for an imaging material in the present invention, itis more advantageous to constitute the front resin sheet as a structureof two or more layers for improving the gloss appearance.

In the supports I and II, preferably, the front resin sheet constitutedas a structure of two or more layers is produced by a melt extrusioncoating method. The front resin sheet is produced by a so-calledco-extrusion coating method in which two or more layers are concurrentlyextruded to coat the base paper, or by a so-called consecutive extrusioncoating method in which a resin layer at least for the lowermost layeris first melt-extruded in one station and a resin layer at least for theuppermost layer is finally melt-extruded in another station. Otherwise,there may be employed a method in which the support which is beingproduced is once taken up and then allowed to pass a resin coating linea plurality of times. In the present invention, preferred is the supportfor an imaging material having a two-layered resin sheet produced by theconsecutive extrusion coating method.

The slit die for the melt extrusion coating is preferably selected froma T-die, an L-die, a fish tail die or a flat die, and the diameter ofthe slit opening is preferably 0.1 mm to 2 mm. The die for themulti-layer extrusion may be any die of a feed block type, amulti-manifold type or a multi-slot type. Although differing dependingupon the kind of a resin, the temperature of the molten film isgenerally preferably 280° C. to 340° C., and the temperature of a resincomposition for the uppermost layer and the temperature of a resincomposition for a resin layer positioned below it may be different. Forexample, when the temperature of the resin composition for the uppermostlayer is set at a temperature 5 to 10° C. lower than the temperature ofthe resin composition positioned below it, the resin layer is improvedin the property of peeling from a cooling roll.

For the front resin sheet and the reverse resin sheet of the support Iand the reverse resin sheet of the support II, the resin having filmformability preferably includes thermoplastic resins such as apolyolefin resin, a polycarbonate resin, a polyester resin, a polyamideresin or a mixture of at least two of theses. In view of coatbility bymelt extrusion, a polyolefin resin and a polyester resin are morepreferred, and a polyethylene resin is particularly preferred. Further,the above resin may be selected from electron-beam-curable resinsdisclosed in JP-B-60-17104.

In the support II, a polyethylene resin is particularly preferred as apolyolefin resin used for forming the front resin sheet.

The above polyethylene resin includes a low-density polyethylene resin,an intermediate-density polyethylene resin, a high-density polyethyleneresin, a linear low-density polyethylene resin, an ultra-low-densitypolyethylene resin, a copolymer of ethylene and α-olefin such aspropylene or butylene, a co-called carboxy-modified polyethylene resinwhich is a copolymer or a graft copolymer of ethylene and acrylic acid,ethyl acrylate or maleic anhydride, a polyethylene resin obtained by ahigh-pressure radical polymerization method using an autoclave reactoror a tubular reactor, a polyethylene resin produced by polymerization inthe presence of a metallocene polymerization catalyst and a polyethyleneresin produced by polymerization in the presence of a metal catalystother than metallocene according to a Ziegler method or a Phillipsmethod. These polyethylene resins may be used alone or in combination.The density, the melt flow rates (MFR, defined under JIS K 6760), themolecular weight and the molecular weight distribution of thepolyethylene resin are not specially limited, while, advantageously, theresin component (or mixture of resins) for constituting the resin sheethas a density of 0.90 to 0.97 g/cm³, an MFR of 0.1 g/10 minutes to 50g/10 minutes, preferably 0.3 g/10 minutes to 40 g/10 minutes.

The polyethylene resin produced by a high-pressure method, preferablyused for the front resin layer of the support I or II includes variouspolyethylene resins having a long-chain branch, produced by ahigh-pressure method using an autoclave reactor or a tubular reactor.Examples of the above polyethylene resins produced by a high pressuremethod include a low-density polyethylene resin, an intermediate-densitypolyethylene resin, a copolymer of ethylene as a main component and anα-olefin such as propylene or butylene and a carboxy-modified ethyleneresin. These polyethylene resins may be used alone or in combination.The density, MFR, the molecular weight and the molecular weightdistribution of the polyethylene resin are not specially limited, whilethe polyethylene resin generally has a density of 0.90 to 0.95 g/cm³ andan MFR of 0.1 to 50 g/10 minutes, preferably 0.4 to 50 g/10 minutes.

The polyethylene resin produced by polymerization in the presence of ametallocene polymerization catalyst, particularly preferably used forthe front resin layer of the support I or II, refers to a resin producedby polymerization in the presence of a polymerization catalyst which isincreased in catalytic activity by combining a zirconium- orhafnium-containing metallocene with, preferably, methylaluminoxane as isdisclosed in PCT Japanese Translation Publication 3-502710,JP-A-3-234718, PCT Japanese Translation Publication 63-501369,JP-A-3-234717 and JP-A-3-234718. Examples of the polyethylene resinproduced by polymerization in the presence of a metallocenepolymerization catalyst include an ultra-low-density polyethylene resin,a low-density polyethylene resin, an intermediate-density polyethyleneresin, a high-density polyethylene resin, a linear low-densitypolyethylene resin, a copolymer of ethylene as a main component and anα-olefin such as propylene or butylene and a carboxy-modifiedpolyethylene resin. These polyethylene resins may be used alone or incombination. The density, MFR, the molecular weight and the molecularweight distribution of the polyethylene resin are not specially limited,while the polyethylene resin generally has a density of 0.87 to 0.97g/cm³ and an MFR of 0.05 to 500 g/10 minutes, preferably 0.08 to 300g/10 minutes.

The polyethylene resin produced by polymerization in the presence of ametal polymerization catalyst other than metallocene, particularlypreferably used for the front resin layer of the support I or II,includes various polyethylene resins produced, e.g., by a Ziegler methodor a Phillips method. The polyethylene resin produced by polymerizationin the presence of a metal polymerization catalyst other thanmetallocene includes an ultra-low-density polyethylene resin, alow-density polyethylene resin, an intermediate-density polyethyleneresin, a high-density polyethylene resin, a linear low-densitypolyethylene resin, a copolymer of ethylene as a main component and anα-olefin such as propylene or butylene and a carboxy-modifiedpolyethylene resin. These polyethylene resins may be used alone or incombination. The density, MFR, the molecular weight and the molecularweight distribution of the polyethylene resin are not specially limited,while the polyethylene resin generally has a density of 0.87 to 0.97g/cm³ and an MFR of 0.05 to 500 g/10 minutes, preferably 0.08 to 300g/10 minutes.

The polyester resin used for the front resin sheet and the reverse resinsheet of the support 1 and for the reverse resin sheet of the support IIincludes a polyethylene terephthalate resin, a polybutyleneterephthalate resin, a polyester-based biodegradable resin, a mixture ofat least two of these and a mixture of at least one of these with apolyethylene. resin. The density and the intrinsic viscosity [η] of thepolyester resin are not specially limited. As a specific example, apolyester resin (trade name “NOVAPEX HS004” supplied by MitsubishiChemical Co., Ltd., melting point 235° C., density 1.33 g/cm³, intrinsicviscosity [η] 0.73 dl/g) is available. Further, a mixture of a polyesterresin with a polyethylene resin can be advantageously used. For example,a mixture (melting point 224° C., supplied by Mitsubishi Chemical Co.,Ltd.) of a polyethylene terephthalate copolymer resin with apolyethylene copolymer resin (melting point 74° C.) graft-modified withmaleic acid is available.

The polycarbonate resin used for the front resin sheet and the reverseresin sheet of the support I and the reverse resin sheet of the supportII includes polycarbonate resins of various grades. Specifically, apolycarbonate resin (trade name: NOVAREX 7022A, density 1.20 g/cm³, MFR12 to 16 g/10 minutes, softening point 160° C. to 190° C.) supplied byMitsubishi Chemical Co., Ltd. is available.

As a polyethylene resin for the reverse side sheet of the support I orII of the present invention, preferred is a compounded resin compositionprepared by pre-melting and pre-mixing 90 to 65 parts by weight of ahigh-density polyethylene resin having an MFR of 10 g/10 minutes to 40g/10 minutes, preferably 10 g/10 minutes to 30 g/10 minutes, and adensity of at least 0.960 g/cm³ and 10 to 35 parts by weight of alow-density or intermediate-density polyethylene resin having an MFR of0.2 g/10 minutes to 3 g/10 minutes, preferably 0.2 g/10 minutes to 1.5g/10 minutes and a density of 0.935 g/cm³ or less. Concerning themolecular weight distribution of the low-density or intermediate-densitypolyethylene resin, preferably, the percentage of a polyethylene resinhaving a molecular weight of at least 500,000 is preferably at least 10%by weight, particularly preferably at least 12% by weight. When thepercentage of a polyethylene resin having a molecular weight of at least500,000 is less than 10% by weight, undesirably, the shapability is poorand in particular, “neck-in” is heavy. The above molecular weight ismeasured by a GPC method using 150-C supplied by Waters Co., Ltd.(columns: GMH-XL HT 8 mmφ×30 cm×3 columns, supplied by Tosoh Corp.,solvent: 1,2,4-trichlorobenzene, temperature 135° C., flow speed: 1ml/min.)

As a polyethylene resin for the reverse resin sheet of the support I orII of the present invention, preferred is a pre-melted and pre-mixedcompounded resin. The compounded resin is prepared by melting and mixingthe low-density or intermediate-density polyethylene resin and thehigh-density polyethylene resin in advance according to a simplemelt-mixing method or a multi-stage melt-mixing method. For example,there is advantageously employed a method in which predetermined amountsof the low-density or intermediate-density polyethylene and thehigh-density polyethylene are melted and mixed optionally together withan antioxidant, a lubricant and the like with an extruder, a twin-screwextruder, a hot roll kneader, a Banbury mixer or a pressure kneader andthe resultant mixture is pelletized.

In the supports I and II of the present invention, the uppermost resinlayer (to be sometimes abbreviated as “upper most layer” hereinafter) ofthe front resin sheet and a resin layer under it (to be sometimesabbreviated as “under resin layer” hereinafter) may have the sameproperties and the same composition or may have different properties anddifferent compositions. The polyethylene resin for the uppermost layerand the polyethylene resin for the under resin layer can be selectedfrom those polyethylene resins having the above density, MFR andmolecular weight values and the above molecular weight distributions,and these resins may be used alone or in combination for each layer.When used in combination, those resins used may have the same propertiesor they may have different properties.

For example, the MFR of a polyethylene resin (including a mixture of atleast two polyethylene resins) used for the uppermost layer may behigher or lower than, or the same as, the MFR of a polyethylene resin(including a mixture of at least two polyethylene resins, used in thissense hereinafter) used for the under resin layer. For example, apolyethylene resin having an MFR of 5 g/10 minutes to 20 g/10 minutesfor the uppermost layer and a polyethylene resin having an MFR of 2 g/10minutes to 10 g/10 minutes for the under resin layer may be used.Further, a polyethylene resin having an MFR of 2 g/10 minutes to 10 g/10minutes for the uppermost layer and a polyethylene resin having an MFRof 5 g/10 minutes to 20 g/10 minutes for the under resin layer may beused. Further, polyethylene resin(s) having the same MFR values may beused for the uppermost layer and the lower resin layer.

Further, the density of a polyethylene resin (including a mixture of atleast two polyethylene resins) used for the uppermost layer may behigher or lower than, or the same as, the density of a polyethyleneresin (including a mixture of at least two polyethylene resins, used inthis sense hereinafter) used for the under resin layer. For example, apolyethylene resin having a density of 0.925 g/cm³ to 0.970 g/cm³ forthe uppermost layer and a polyethylene resin having a density of 0.870g/cm³ to 0.925 g/cm³ for the under resin layer may be used. Further, apolyethylene resin having a density of 0.870 g/cm³ to 0.925 g/cm³ forthe uppermost layer and a polyethylene resin having a density of 0.925g/cm³ to 0.970 g/cm³ for the under resin layer may be used. Further,polyethylene resin(s) having the same density values may be used for theuppermost layer and the lower resin layer.

Further, at least one polyethylene resin whose melting point is higheror lower than, or the same as, the melting point of a polyethylene resinused for the under resin layer may be used for the uppermost layer. Forexample, a polyethylene resin having a melting point of at least 115° C.for the uppermost layer and a polyethylene resin having a melting pointof less than 115° C. for the under resin layer may be used. Further, apolyethylene resin having a melting point of less than 115° C. for theuppermost layer and a polyethylene resin having a melting point of atleast 115° C. for the under resin layer may be used. Further,polyethylene resin(s) having the same melting points may be used for theuppermost layer and the lower resin layer.

In view of the effects of the present invention, i.e., the achievementsof remarkable effects on improvements in the gloss appearance of animaging material and a print thereon and the property of peeling of thesupport, the following multi-layered front resin sheet of the supports Ior II of the present invention is particularly preferred. That is, thefront resin sheet has the uppermost layer composed of at least onepolyethylene resin having a higher density than a polyethylene resin forthe lower resin layer, at least one polyethylene resin having a highermelting point than a polyethylene resin for the lower resin layer, or atleast one polyethylene resin having a higher density and a highermelting point than a polyethylene resin for the lower resin layer.

The front resin sheet of the support I or II of the present inventionand the optionally provided reverse resin sheet of the support I or IImay contain various additives. For improving the whiteness of thesupport and the sharpness of an image, it is preferred to incorporate atitanium dioxide pigment disclosed in JP-B-60-3430, JP-B-63-11655,JP-B-1-38291, JP-B-1-38292 and JP-A-1-105245. In addition to thetitanium dioxide pigment, the front resin sheet and the reverse resinsheet may contain a white pigment such as zinc oxide, talc or calciumcarbonate, a fatty acid amide such as stearic acid amide or arachic acidamide as a releasing agent, a fatty acid metal salt such as zincstearate, calcium stearate, aluminum stearate, magnesium stearate, zincpalmitate, zinc myristate or calcium palmitate as a dispersing agent fora pigment and a releasing agent, an antioxidant such as hindered phenol,hindered amine, phosphorus-containing antioxidant or a sulfur-containingantioxidant disclosed in JP-A-1-105245, a blue pigment or dye such asCobalt Blue, Ultramarine, Cerulein Blue or Phthalocyanine Blue, amagenta pigment or dye such as Cobalt Violet, Phosphite Violet orManganese Violet, a fluorescent brightener disclosed in JP-A-2-254440,and an ultraviolet absorbent. The above additives are properly combinedand incorporated. Preferably, these additives are incorporated as amaster batch or a compound. In view of effective improvements in thesharpness or whiteness of a print and the heat resistance, lightresistance and peeling properties of the support for an imagingmaterial, it is preferred to incorporate higher concentrations of awhite pigment such as titanium oxide and other additives such as afluorescent brightener, a colorant pigment, a colorant dye, anantioxidant, an ultraviolet absorbent and a releasing agent into theuppermost layer than to the under resin layer.

In the supports I and II of the present invention, preferably, the basepaper is subjected to activation treatment such as corona dischargetreatment or flaming treatment before the base paper is coated withcompositions for the front and reverse resin sheets. Further, asdescribed in JP-B-61-42254, an ozone-containing gas may be blown to amolten resin composition which is to be brought into contact with thebase paper, before the running base paper is coated with the resinlayer. The front and reverse resin sheets are respectively coated on thebase paper preferably by continuous extrusion, a so-called tandemextrusion coating method. Further, the reverse resin sheet may be amulti-layered coating having at least two layers as well. The frontresin sheet of the support for an imaging material may be treated so asto have a gloss surface, a finely roughened surface disclosed inJP-B-62-19732, a matted surface or a meshed surface, and preferably, thereverse resin sheet is generally treated so as to have a gloss-freesurface.

In each of the supports I and II of the present invention, the thicknessof the entire front resin sheet is advantageously 8 to 100 μm,preferably 12 to 60 μm, particularly preferably 18 to 40 μm. Althoughnot specially limited, the thickness of the lowermost layer of the frontresin sheet of the support I and the thickness of the lowermost resinlayer of the front resin layer of the support II when the front resinlayer has a multi-layered structure, are preferably at least 25%, morepreferably at least 39%, particularly preferably at least 50%, of thefront resin sheet, in view of the effect on improvement in the glossappearance of an imaging material and a print thereon. The reversesurface of the base paper is preferably coated with the reverse resinsheet composed mainly of a resin having film formability. The aboveresin is preferably a polyethylene resin. The thickness of the reverseresin sheet is preferably well-balanced with the thickness of the frontresin sheet concerning curl resistance. The thickness of the reverseresin sheet is advantageously 8 to 100 μm, preferably 12 to 60 μm.

The support III for an imaging material (to be sometimes referred to as“support III” hereinafter), provided by the present invention, will beexplained below.

In the support II of the present invention, the front resin sheet is amulti-layered resin sheet composed of an upper layer (surface layer) Aand a lower layer (B) (which refers to one layer or layers present underthe surface layer). The upper layer (A) is required to contain at least50% by weight of a polyethylene resin (a) having a density of at least0.940 g/cm³. When the content of the polyethylene resin (a) is less than50% by weight, there is no sufficient effect on the improvement of thegloss appearance of the imaging material and a print thereon. In view ofthe effect on the above improvement, the above content is preferably atleast 60% by weight, particularly preferably at least 70% by weight.Further, when the density of the polyethylene resin (a) is less than0.940 g/cm³, there is no sufficient effect on the improvement of thegloss appearance of the imaging material and a print thereon. In view ofthe effect on the above improvement, the above density is preferably atleast 0.945 g/cm³, particularly preferably at least 0.950 g/cm³.

The above polyethylene resin (a) can be selected from variouspolyethylene resins, and polyethylene resins having various densityvalues, melt flow rates, molecular weights and molecular weightdistributions may be used alone or in combination. When a mixture ofpolyethylene resins is used, it is sufficient that the mixture shouldhave a density (calculated density) of at least 0.940 g/cm³.

The thickness of the layer (A) is required to be equivalent to, orsmaller than, the thickness of the multi-layered resin sheet. When theabove thickness exceeds 50%, the effects of the present invention arenot sufficiently exhibited. In view of the effects, the thickness of thelayer (A) is preferably equivalent to, or smaller than, 35%,particularly preferably 20%, of the thickness of the multi-layered resinsheet.

In the front multi-layered resin sheet of the support III of the presentinvention, the polyethylene resin having a density of at least 0.94g/cm³, contained in the upper layer (A), includes a polyethylene resinproduced in the presence of a metallocene polymerization catalyst, apolyethylene resin produced in the presence of a metal catalyst otherthan the metallocene polymerization catalyst and a mixture of them.

The polyethylene resin produced by polymerization in the presence of ametallocene polymerization catalyst refers to a resin produced bypolymerization in the presence of a polymerization catalyst which isincreased in catalytic activity by combining a zirconium- orhafnium-containing metallocene with, preferably, methylaluminoxane as isdisclosed in PCT Japanese Translation Publication 3-502710, JP-A-60-356,PCT Japanese Translation Publication 63-501369, JP-A-3-234717 andJP-A-3-234718. Examples of the polyethylene resin produced bypolymerization in the presence of the above metallocene polymerizationcatalyst include an intermediate-density polyethylene resin, ahigh-density polyethylene resin, a copolymer of ethylene as a maincomponent and an α-olefin such as propylene or butylene and acarboxy-modified polyethylene resin. These polyethylene resins may beused alone or in combination. The density, the melt flow rate, themolecular weight and the molecular weight distribution of thepolyethylene resin are not specially limited, while the polyethyleneresin generally has a density of 0.94 to 0.97 g/cm³, preferably 0.950 to0.970 g/cm³, particularly preferably 0.960 to 0.970 g/cm³ and a meltflow rate of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10minutes.

The polyethylene resin produced by polymerization in the presence of ametal polymerization catalyst other than metallocene, particularlypreferably used for the above front resin layer (A), includes variouspolyethylene resins produced, e.g., by a Ziegler method or a Phllipsmethod. The polyethylene resin produced by polymerization in thepresence of a metal polymerization catalyst other than metalloceneincludes an intermediate-density polyethylene resin, a high-densitypolyethylene resin, a copolymer of ethylene as a main component and anα-olefin such as propylene or butylene and a carboxy-modifiedpolyethylene resin. These polyethylene resins may be used alone or incombination. The density, the melt flow rate, the molecular weight andthe molecular weight distribution of the polyethylene resin are notspecially limited, while the polyethylene resin generally has a densityof 0.94 to 0.97 g/cm³, preferably 0.950 to 0.970 g/cm³, particularlypreferably 0.960 to 0.970 g/cm³ and a melt flow rate of 0.05 to 500 g/10minutes, preferably 0.08 to 300 g/10 minutes.

In the support III of the present invention, for improving the curlresistance of the imaging material and its print and the shapability ofthe resin composition for the upper layer (A), it is preferred to usethe above polyethylene resin having a density of at least 0.940 g/cm³and a polyethylene resin (to be described later) having a density ofless than 0.940 g/cm³, preferably a density equivalent to, or smallerthan, 0.928 g/cm³, more preferably a density equivalent to, or smallerthan, 0.924 g/cm³, particularly preferably a density equivalent to, orsmaller than, 0.918 g/cm³. The term “shapability” in the presentspecification refers to overall shapability including the degree of“neck-in”, film breakage depending upon the degree of drawdown, theunstableness of flow caused by surging or draw resonance, the degree ofoccurrence of streaks on a molten resin film and the degree ofoccurrence of “fouling” in a die lip.

The lower layer (B) of the multi-layered resin sheet is required tocontain a largest amount of a polyethylene resin (b) having a density ofless than 0.940 g/cm³ among polyethylene-based resins in the layer (B).When the density of the above polyethylene resin (b) is 0.940 g/cm³ orgreater, there is no sufficient effect on the improvement in curlresistance. In view of the effect on the above improvement, the abovedensity is preferably 0.928 g/cm³ or lower, more preferably 0.924 g/cm³or lower, particularly preferably 0.921 g/cm³.

The above polyethylene resin (b) can be selected from variouspolyethylene resins, and the melt flow rate, the molecular weight andthe molecular weight distributions of the polyethylene resin (b) are notspecially limited. Various polyethylene resins may be used alone or incombination. When a mixture of polyethylene resins is used, it issufficient that the mixture should have a density (calculated density)of less than 0.940 g/cm³.

The polyethylene resin having a density of less than 0.940 g/cm³, usedfor the lower layer (B), includes a polyethylene resin produced by ahigh-pressure method, a polyethylene resin produced by polymerization inthe presence of a metallocene polymerization catalyst, a polyethyleneresin produced by polymerization in the presence of a metal catalystother than metallocene and a mixture of at least two of these.

The above polyethylene resin having a density of less than 0.940 g/cm³for the lower layer (B), produced by a high-pressure method, includesvarious polyethylene resins having a long-chain branch, produced by ahigh-pressure method using an autoclave reactor or a tubular reactor.Examples of the polyethylene resins produced by a high-pressure methodinclude a low-density polyethylene resin, an intermediate-densitypolyethylene resin, a copolymer of ethylene as a main component and anα-olefin such as propylene or butylene and a carboxy-modifiedpolyethylene resin. These polyethylene resins may be used alone or incombination. The melt flow rate, the molecular weight and the molecularweight distribution of the polyethylene resin are not specially limited,while the polyethylene resin generally has a density of 0.90 to lessthan 0.94 g/cm³, preferably 0.90 to 0.928 g/cm³, more preferably 0.90 to0.924 g/cm³, particularly preferably 0.90 to 0.921 g/cm³ and a melt flowrate of 0.1 to 50 g/10 minutes, preferably 0.4 to 50 g/10 minutes.

The polyethylene resin having a density of less than 0.940 g/cm³ for thelower layer (B), produced by polymerization in the presence of ametallocene polymerization catalyst is a resin produced bypolymerization in the presence of a polymerization catalyst which isincreased in catalytic activity by combining a zirconium- orhafnium-containing metallocene with, preferably, methylaluminoxane as isdisclosed in PCT Japanese Translation Publication 3-502710, JP-A-60-356,PCT Japanese Translation Publication 63-501369, JP-A-3-234717 andJP-A-3-234718. Examples of the polyethylene resin produced bypolymerization in the presence of the above metallocene polymerizationcatalyst include an ultra-low-density polyethylene resin, a low-densitypolyethylene resin, an intermediate-density polyethylene resin, a linearlow-density polyethylene resin, a copolymer of ethylene as a maincomponent and an α-olefin such as propylene or butylene and acarboxy-modified polyethylene resin. These polyethylene resins may beused alone or in combination. The density, the melt flow rates, themolecular weight and the molecular weight distribution of thepolyethylene resin are not specially limited, while the polyethyleneresin generally has a density of 0.87 to less than 0.94 g/cm³,preferably 0.870 to 0.928 g/cm³, more preferably 0.870 to 0.924 g/cm³,particularly preferably 0.870 to 0.921 g/cm³ and a melt flow rates of0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.

The polyethylene resin having a density of less than 0.940 g/cm³ for thelower layer (B), produced by polymerization in the presence of a metalpolymerization catalyst other than a metallocene polymerization catalystincludes various polyethylene resins produced, e.g., by a Ziegler methodor a Phllips method. The polyethylene resin produced by polymerizationin the presence of a metal polymerization catalyst other thanmetallocene includes an ultra-low-density polyethylene resin, alow-density polyethylene resin, an intermediate-density polyethyleneresin, a linear low-density polyethylene resin, a copolymer of ethyleneas a main component and an α-olefin such as propylene or butylene and acarboxy-modified polyethylene resin. These polyethylene resins may beused alone or in combination. The density, the melt flow rate, themolecular weight and the molecular weight distribution of thepolyethylene resin are not specially limited, while the polyethyleneresin generally has a density of 0.87 to less than 0.94 g/cm³,preferably 0.870 to 0.928 g/cm³, more preferably 0.870 to 0.924 g/cm³,particularly preferably 0.870 to 0.921 g/cm³ and a melt flow rate of0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.

When at least two polyethylene resins having different melt flow ratesare used in combination for the upper layer or the lower layer of themulti-layered sheet of the support III, it is preferred to use thesepolyethylene resins as a compounded resin composition prepared bymelting and mixing them in advance. For example, when a polyethyleneresin having a melt flow rate of 5 to 40 g/10 minutes and a polyethyleneresin having a melt flow rate of 0.2 to 4.5 g/10 minutes are used incombination, it is preferred to use these polyethylene resins as apre-melted and pre-mixed compounded resin composition. The so-preparedcompounded resin composition is preferred in view of shapability, filmuniformity and the prevention of clotting of a non-uniform resin calleda resin gel. The compounded resin composition can be prepared by variousmethods, for example, a method in which at least two polyethylene resinsare melted and mixed optionally together with other thermoplastic resinand additives such as an antioxidant, a lubricant and the like with akneading extruder, a hot roll mill, a Banbury mixer or a pressurekneader and the resultant mixture is pelletized.

Although not specially limited, the melt flow rate of the polyethyleneresin components as a total in the resin composition for the upper layer(A) or the lower layer (B) of the multi-layered resin sheet ispreferably 2 to 20 g/10 minutes, more preferably 3 to 15 g/10 minutes inview of the melt extrusion coatability of the resin composition,shapability and the effect on the improvement in gloss appearance.

The reverse surface of the support III of the present invention ispreferably coated with a resin sheet (C) containing a resin (c) havingfilm formability. The resin (c) is preferably selected fromthermoplastic resins such as a polyolefin resin, a polycarbonate resinand a polyamide resin. Of these, in view of melt extrusion coatability,a polyolefin resin is more preferred, and a polyethylene resin isparticularly preferred. Further, an electron-beam-curable resindisclosed in JP-B-60-17104 may be also used.

The polyethylene resin preferred for the reverse resin sheet of thesupport III is preferably a compounded resin composition which isprepared by pre-melting and pre-mixing 90 to 65 parts by weight of ahigh-density polyethylene resin having a melt flow rate of 10 g/10minutes to 40 g/10 minutes and a density of at least 0.960 g/cm³ and 10to 35 parts by weight of an low-density or intermediate polyethyleneresin having a melt flow rate of 0.2 g/10 minutes to 3 g/10 minutes anda density of at least 0.935 g/cm³ or less.

As already described, the front multi-layered resin sheet of the supportIII has a structure of at least two layers, the upper layer (A)containing at least 50% by weight of the polyethylene resin (a) and thelower layer (B) containing a largest amount of the polyethylene resin(b).

The “upper” and “lower” in the present invention shows arelative-positional relationship in which the upper layer (A) is farfrom the base paper and the lower layer (B) is close to the base paper.In the constitution of the support III of the present invention, in viewof the effects of the present invention, preferably, the upper layer isthe uppermost layer, and the lower layer is the lowermost layer, andmore preferably, the lower layer (B) constitutes an intermediate layerand the lowermost layer.

The resin layer of the upper layer (A) or the lower layer (B) maycontain other resin (other than the resins (a) and (b)), e.g., ahomopolymer such as a polyethylene resin, polybutene or a polypentene, acopolymer of at least two α-olefins such as an ethylene-butylenecopolymer or a polyester resin so long as the effects of the presentinvention are not impared and so long as the requirements of the presentinvention are satisfied.

The front resin sheet of the support III of the present invention mayhave a multi-layered structure of two layers or more, while, forefficiently achieving the object of the present invention, a two-layeredor three-layered structure is preferred, and a three-layered structureof the uppermost layer, an intermediate layer and the lowermost layer isparticularly preferred. The support III of the present invention isproduced by a so-called melt extrusion coating method in which a resincomposition molten under heat is cast onto a running base paper to coatit. For the above production, there may be employed a so-calledco-extrusion coating method in which two or more resin layers for thesupport III are formed by concurrent-extrusion coating, or there may beemployed a so-called consecutive extrusion coating method in which aresin layer for the lowermost layer is formed by melt extrusion coatingin one station and then at least a resin layer for the uppermost layeris formed by melt extrusion coating in another station. In the presentinvention, when the front resin sheet has a structure of at least threelayers, in view of the effect on improvement in gloss appearance of theimaging material and a print thereon, preferred is a support produced bya consecutive extrusion coating method in which at least resin layer forthe lowermost layer is formed by melt extrusion coating, and then resinlayers for the intermediate layer and the uppermost layer are formed byconcurrent extrusion with another two-layer co-extruder. Further, whenthe consecutive extrusion coating is carried out, the resin layer for atleast the lowermost layer may be subjected to activation treatment suchas corona discharge treatment.

The slit die used for the melt extrusion coating is preferably selectedfrom a T-die, an L-die, a fish tail die or a flat die, and the diameterof the slit opening is preferably 0.1 mm to 2 mm. The die for themulti-layer co-extrusion may be any die of a feed block type, amulti-manifold type or a multi-slot type. The temperature of the moltenfilm is preferably 270° C. to 340° C., and the temperature of a resincomposition for the uppermost layer and the temperature of a resincomposition for a resin layer positioned under it may be different. Forexample, when the temperature of the resin composition for the uppermostlayer is set at a temperature 5 to 20° C. lower than the temperature ofthe resin composition for a resin layer under it, the resin layer isimproved in the property of peeling from a cooling roll.

In the support III of the present invention, the total thickness of thefront resin sheet composed of at least two layers is advantageously 8 to100 μm, preferably 12 to 60 μm, particularly preferably 18 to 40 μm.Further, in view of the effects on the improvements in gloss appearanceof the imaging material and a print thereon and the curl resistance, thethickness of the upper layer (A) is preferably 35% or less, particularlypreferably 20% or less, of the thickness of the front multi-layeredresin sheet, although it is not specially limited. Further, the reversesurface of the base paper is preferably coated with a reverse resinsheet (C) composed mainly of a resin (c) having film formability. Theresin (c) is preferably a polyethylene resin. The thickness of thereverse resin sheet (C) is particularly preferably determined so as tobe well-balanced with the thickness of the front resin sheet concerningcurl resistance. The thickness of the reverse resin sheet (C) isgenerally advantageously 8 to 100 μm, preferably 12 to 60 μm.

In the support III of the present invention, it is preferred to subjectthe base paper to activation treatment such as corona dischargetreatment or flaming treatment before the resin composition for thefront and reverse resin sheets are coated on the base paper. Further, asdescribed in JP-B-61-42254, an ozone-containing gas may be blown to amolten resin composition which is to be brought into contact with thebase paper, before the running base paper is coated with the resinlayer. The front and reverse resin sheets are respectively coated on thebase paper preferably by continuous extrusion, a so-called tandemextrusion coating method. Further, the reverse resin sheet may be amulti-layered coating having at least two layers as well. The frontresin sheet of the support III for an imaging material may be treated soas to have a mirror surface, a gloss surface or a finely roughenedsurface disclosed in JP-B-62-19732, and preferably, the reverse resinsheet is generally treated so as to have a gloss-free surface.

The front resin sheet and the optionally provided reverse resin sheet ofthe support III of the present invention may contain various additives.Examples of the additives include those specified with regard to thesupports I and II.

The support III of the present invention uses a base paper composedmainly of a natural pulp. The fiber length of the above natural pulpwhich is beaten before chemicals for paper are added is 0.45 mm to 0.65mm. In view of the effect on improvements in the gloss appearance of animaging material and a print thereon and the strength of stiffnessthereof, the above fiber length is preferably 0.48 mm to 0.62 mm, morepreferably 0.50 mm to 0.59 mm, particularly preferably 0.53 mm to 0.59mm. Specifically, a natural pulp having a fiber length in the aboverange can be prepared by selecting a proper pulp, beating the pulp witha beating machine having a proper structure under a series of combinedexperimental conditions with regard to beating conditions such as abeating time, a pulp concentration and a beating power and measuring asampled pulp slurry for a pulp fiber length. Further, as a condition ofbeating the pulp, it is preferred to optimize the balance between thecutting-based beating and the beating in a viscous state, and thefreeness of the beaten pulp is preferably 200 ml to 400 ml, morepreferably 230 ml to 370 ml, particularly preferably 260 ml to 340 ml.

The base paper for the support III of the present invention ispreferably a natural pulp paper composed mainly of a natural pulp.Further, the base paper may be a mixed paper composed of a natural pulpas a main component and a synthetic pulp or a synthetic pulp. As thenatural pulp, it is preferred to use a properly selected natural pulpdisclosed in JP-A-58-37642, JP-A-60-67940, JP-A-60-69649 andJP-A-61-35442. The natural pulp can be advantageously selected from aconifier pulp, a broad-leaved tree pulp and a mixture of a conifer pulpand broad-leaved tree pulp which are subjected to general bleachingtreatment such as treatment with hydrochloric acid, hypochlorite orchlorine dioxide, alkali-extraction or -treatment and optional bleachingtreatment with hydrogen peroxide or oxygen, or a combination of thesetreatments. Further, various pulps such as a kraft pulp, a sulfite pulpand a soda pulp may be used, while a broad-leaved tree bleached craft isadvantageously used.

In the base paper composed mainly of a natural pulp, used for thesupport III of the present invention, various additives may be added toa paper material slurry when the slurry is prepared. Examples of theseadditives include those specified with regard to the supports I and II.

Further, the base paper composed mainly of a natural pulp, used for thesupport III of the present invention, may be impregnated or coated witha composition containing any one of a water-soluble polymer, ahydrophilic colloid and a latex, an antistatic agent and other additiveby size press, tub size press or coating such as blade coating or airknife coating. Examples of components of the above composition includethose specified with regard to the supports I and II.

The thickness of the base paper for the support III is not speciallylimited, while the basis weight of the base paper is preferably 30 g/m²to 250 g/m², and the basis weight of the base paper for a photographicprint is more preferably 70 g/m² to 220 g/m², particularly preferably150 g/m² to 200 g/m².

In the base paper composed mainly of a natural pulp for the support IIIof the present invention, the central plane average roughness SRa of thefront surface of the base paper measured in a paper-making directionwith a stylus-applied three-dimensional surface roughness tester at acut-off value of 0.8 mm is preferably 1.5 μm or less, more preferably1.4 μm or less, particularly preferably 1.3 μm or less.

According to studies by the present inventors, specifically, it has beenfound that the base paper having a central plane average roughness SRaof 1.5 μm or less can be obtained by the following method, preferably bya combination of at least two methods below, more preferably by acombination of at least three methods below.

(1) As a natural pulp, it is preferred to use a broad-leaved treebleached kraft pulp or a combination of a broad-leaved tree bleachedkraft pulp and a broad-leaved tree bleached sulfite pulp. Further, thereis used a natural pulp which is beaten so as to have an optimum fiberlength and an optimum freeness as described above.

(2) During the drying of a wet paper, a bulk density increasing press isused. Specifically, a wet paper is subjected to a multi-stage bulkdensity increasing press as disclosed, for example, in JP-A-3-29945.

(3) Prior to forming an image-forming layer, the surface of the basepaper where an image-forming layer is to be formed is coated with alayer formed of a coating composition containing a binder, preferably awater-soluble polymer, a hydrophilic colloid or a polymer latex.Specifically, the surface of the base paper where an image-forming layeris to be formed is coated with a coating composition containing awater-soluble polymer, a hydrophilic colloid or a polymer latex by sizepress, tub size press, blade coating or air knife coating to form alayer having a solid coating amount of at least 2 g/cm², preferably atleast 5 g/cm². Further, the layer formed by the above coating preferablycontains an inorganic or organic pigment for further improving the layerin flatness.

(4) The produced base paper is calendered in at least two lines by meansof a machine calender, a super calender or a hot calender. Specifically,in the first line, the base paper is treated with a machine calender ora hot machine calender or both, and in the second line and thereafter,the base paper is treated with a machine calender, a hot calender or ahot soft calender as described in JP-A-4-110938. It is particularlypreferred to treat the base paper with a combination of these. Further,the calender treatment in the second line and thereafter is preferablycarried out on machine after the base paper is produced.

After the surface of the front resin sheet of any one of the supports I,II and III of the present invention is subjected to activation treatmentsuch as corona discharge treatment or flaming treatment, an undercoatlayer may be formed on the surface as disclosed in JP-A-61-84643,JP-A-1-92740, JP-A-1-102551 or JP-A-1-166035. Further, after the surfaceof the back resin sheet of any one of the supports I, II and III of thepresent invention is subjected to activation treatment such as coronadischarge treatment or flaming treatment, a back coating layer may beformed on the surface for antistatic performance, and the like. The backcoating layer may contain a proper combination of an inorganicantistatic agent, an organic antistatic agent, a hydrophilic binder, alatex, a curing agent, a pigment and a surfactant disclosed inJP-B-52-18020, JP-B-57-9059, JP-B-57-53940, JP-B-58-58859,JP-A-59-214849 and JP-A-58-184144.

Various photograph-constituting layers are formed on the supports I, IIand III for imaging materials, provided by the present invention, andthe supports I, II and III are used in a variety of fields including aphotograph printing paper, a monochrome photograph printing paper, aphotocomposition printing paper, a copy printing paper, a reversalphotograph material, a negative or positive imaging material by a silversalt diffusion transfer method and a printing material. For example, anemulsion layer of a silver chloride, silver bromide, silverchlorobromide, silver iodide or silver cloroiodide may be formedthereon. A color coupler is contained in a silver halide emulsion layerto form a silver halide color photograph-constituting layers. A layerfor constituting a photograph by a silver salt diffusion method may beformed thereon. As a binder for the above photograph-constitutinglayers, there may be used hydrophilic polymer materials such aspolyvinyl pyrrolidone, polyvinyl alcohol, a sulfate ester compound ofpolysaccharide and the like, besides generally used gelatin. Further,the above photograph-constituting layers may contain various additives.Examples of the additive include sensitizing dyestuffs such as cyaninedyestuff and merocyanine dyestuff, chemically sensitizing agents such asa water-soluble gold compound and a sulfur compound, anti-fogging agentsor stabiliers such as a hydroxy-trizaolopyrimidine compound and amercapto-heteocyclic compound, film-curing agents such as formalin, avinyl sulfone compound, an aziridine compound and an active halogencompound, application aids such as alkylbenzenesulfonate andsulfosuccinate, pollution preventers such as a dialkylhdyroquinonecompound, a fluorescent brightener, a sharpness-improving dyestuff, anantistatic agent, a pH adjuster and a fogging agent. Further,water-soluble iridium and a water-soluble rhodium compound may beincorporated when silver halide is formed and dispersed.

A photographic material using the support I, II or III of the presentinvention can be subjected to treatments such as exposure, development,termination, fixing, bleaching and stabilization depending upon thephotographic material as described in “Photographic PhotosensitiveMaterials and Handling Method” (Syashin Gijutsu Koza 2, MIYAMOTO Goro,Kyoritsu Publishing Co. Japan). Further, a multi-layered silver halidecolor photographic material may be treated with a developer solutioncontaining development promoters such as benzyl alcohol, thallium saltand phenidone, or it may be treated with a developer solutionsubstantially containing no benzyl alcohol.

The supports I, II and III for imaging materials, provided by thepresent invention, on which various thermal transfer type heat transferrecord receiving layers are formed, can be used as various thermaltransfer type heat transfer record receiving materials. The syntheticresin which can be used for forming the above thermal transfer type heattransfer record receiving layers includes resins having an ester bondsuch as a polyester resin, a polyacrylate ester resin, a polycarbonateresin, a polyvinyl acetate resin, a polyvinyl butyral resin, a styreneacrylate resin and a vinyltoluene acrylate resin, resins having aurethane bond such as a polyurethane resin, resins having an amide bondsuch as a polyamide resin, resins having a urea bond such as a urearesin, and other resins such as a polycarprolactam resin, a styreneresin, a polyvinyl chloride resin, a vinyl chloride-vinyl acetatecopolymer resin and a polyacrylonitrile resin. A mixture or a copolymerof these may be also used.

In the present invention, the above thermal transfer type heat transferrecord receiving layer may also contain a releasing agent and a pigmentin addition to the above resin(s). The releasing agent includes solidwaxes such as polyethylene wax, amide wax and Teflon powder, afluorine-containing or phosphate ester-containing surfactant andsilicone oil. Of these releasing agents, silicone oil is the mostpreferred. The silicone oil may be in the form of an oil, while acurable silicone oil is preferred. The curable silicone oil includesreaction-curable, photo-curable and catalyst-curable silicone oils,while a reaction-curable silicone oil is the most preferred. Thereaction-curable silicone oil includes amino-modified silicone oil andepoxy-modified silicone oil. The content of the above reaction-curablesilicone oil in the receiving layer is preferably 0.1 to 20% by weight.The above pigment is preferably selected from extender pigments such assilica, calcium carbonate, titanium oxide and zinc oxide. The thicknessof the receiving layer is preferably 0.5 to 20 μm, more preferably 2 to10 μm.

The supports I, II and III for imaging materials, provided by thepresent invention, can be used as supports on which various inkreceiving layers are formed. The ink receiving layer may contain abinder for improving the drying capability of an ink and for improvingthe sharpness (clearness) of an image. Specific examples of the binderinclude various gelatins such as lime-treated gelatin, acid-treatedgelatin, enzyme-treated gelatin, a gelatin derivative, modified gelatinprepared by reacting gelatin with an anhydride of dibasic acid such asphthalic acid, maleic acid or fumaric acid, polyvinyl alcohols havingvarious saponification degrees, carboxy-modified, cation-modified oramphoteric polyvinyl alcohol and a derivative thereof, starches such asoxidized starch, cationized starch, etherified startch, cellulosederivatives such as carboxymethyl cellulose and hydroxyethyl cellulose,synthetic polymers such as polyvinylpyrrolidone, polyvinylpyridiumhalide, sodium polyacrylate, acrylate-methacrylate copolymer salt,polyethyelene glycol, polypropylene glycol, polyvinyl ether, alkylvinylether-maleic anhydide copolymer, styrene-maleic anhydride copolymer andsalt thereof and polyethyleneimine, conjugated diene copolymer latexessuch as styrene-butadiene copolymer and methyl methacrylate-butadienecopolymer, vinyl acetate polymer latexes such as polyvinyl acetate,vinyl acetate-maleate copolymer, vinyl acetate-acrylate copolymer andethylene-vinyl acetate copolymer, latexes of acrylate polymers orcopolymers such as acrylate polymer, methacrylate polymer,ethylene-acrylate copolymer and styrene-acrylate copolymer, vinylidenechloride copolymer latexes, functional-group-modified polymer latexesprepared by modifying the above polymers with a monomer containing afunctional group such as a carboxyl group, water-based adhesivesincluding thermosetting synthetic resins as a melamine resin and a urearesin, synthetic resin adhesives such as polymethyl methacrylate, apolyurethane resin, an unsaturated polyester resin, vinyl chloride-vinylacetate copolymer, polyvinyl butyral and an alkyd resin, and inorganicbinders such as alumina sol and silica sol disclosed in JP-A-3-24906,JP-A-3-281383 and Japanese Patent Application No. 4-240725. The abovebinders may be used alone or in combination.

The ink receiving layer of the inkjet recording material in the presentinvention may contain other additives in addition to the binder.Examples of the additives include surfactants including anionicsurfactants such as long-chain alkylbenzenesulfonate and long-chain,preferably branched, alkylsulfosuccinate, nonionic surfactants such aspolyalkylene oxide ether of lone-chain, preferably branched, alkylgroup-containing phenol and polyalkylene oxide ether of long-chain alkylalcohol and fluorinated surfactants disclosed in JP-B-47-9303 and U.S.Pat. No. 3,589,906, silane coupling agents such asγ-aminopropyltriethoxysilane and N-β(aminoethyl) γ-aminopropyltrimethoxysilane, polymer curing agents such as an active halogencompound, a vinylsulfone compound, an aziridine compound, an epoxycompound, an acryloyl compound and an isocyanate compound, antisepticssuch as p-hydroxybenzoate compounds disclosed in JP-A-1-102551, abenzthiazolone compound and an isothiazolone compound, colorant pigmentsdisclosed in JP-A-63-204251 and JP-A-1-266537, colorant dyes,fluorescent brighteners, yellowing preventers such as sodiumhydroxymethanesulfonate and sodium p-toluenesulfonate, ultravioletabsorbents such as a benzotriazole compound having ahydroxy-dialkylphenyl group on the 2-position, antioxidants such aspoly-hindered-phenol compounds disclosed in JP-A-1-105245, handwritablematerials such as organic or inorganic fine particles of starch powder,barium sulfate or silicon dioxide having a particle diameter of 0.2 to 5μm and organopolysiloxane compounds disclosed in JP-A-4-1337, pHadjusters such as sodium hydroxide, sodium carbonate, sulfuric acid,phosphoric acid and citric acid, octyl alcohol and a silicon-containinganti-foamer. The above additives are used in proper combination.

The supports for imaging materials, provided by the present invention,can provide imaging materials and prints thereon which have high glossappearance and are free of non-uniformity in gloss. Further, thesupports are improved in the properties of peeling from a cooling rolland are free from the occurrence of non-uniform peeling. Moreover, thesupports have excellent curl resistance and strong stiffness, and thesupports can be stably produced at a high speed and are thereforeexcellent in economic performance.

The present invention will be explained with reference to Exampleshereinafter, while the present invention shall not be limited byExamples.

EXAMPLES 1-4 AND COMPARATIVE EXAMPLES 1-5

A broad-leaved tree pulp was adjusted to a concentration of 4% by weightin terms of an absolute dry weight and beaten so as to have a pulp fiberlength of 0.6 mm and a Canadian Standard freeness of 350 ml. After thebeating, 3 parts by weight of cationized starch, 0.2 part by weight ofanionized polyacrylamide, 0.4 part by weight (as ketene dimer content)of an alkylketene dimer emulsion, 0.4 part by weight of a polyamideepichlorohydrin resin, and proper amounts of a fluorescent brightener, ablue dye and a red dye were added to 100 parts by weight of the abovepulp, to prepare a paper material slurry. Then, part of the papermaterial slurry was placed on a Fourdriner paper machine running at aspeed of 200 m/minute to form a single layer, and the remaining papermaterial slurry was placed on a Fourdriner paper machine running at aspeed of 200 m/minute to form two layers at two levels of an upper andlower layer balance, and webs were formed with applying properturbulence. In a wet part, each web was subjected to three-stage wetpress at a linear pressure adjusted in the range of 15 to 100 kgf/cm,and then treated with a smoothing roll. In a subsequent drying part,each web was subjected to two-stage bulk density increasing press at alinear pressure adjusted in the range of 30 to 70 kgf/cm and then dried.Then, during the drying, a size press solution containing 4 parts byweight of carboxy-modified polyvinyl alcohol, 0.05 part by weight of afluorescent brightener, 0.002 part by weight of a blue dye, 4 parts byweight of sodium chloride and 92 parts by weight of water was used forsize-pressing at a speed of 25 g/cm², and the webs were dried such thatthe base papers to be finally obtained had a water content of 8% byweight in terms of an absolute dry water content. The webs weremachine-calendered at a linear pressure of 70 kgf/cm to obtain threekinds of base paper for supports for imaging materials, these kinds ofthe base paper having a basis weight of 170 g/m², a density of 1.04g/cm³ and a film thickness non-uniformity index Rpy as shown in Table 1.

The surface (reverse surface) of each base paper, opposite to thesurface where an image-forming layer was to be formed, was subjected tocorona discharge treatment, and then, the following resin composition(R1) was coated on the reverse surface of each base paper to form aresin layer having a thickness of 20 μm by melt extrusion coating at aresin temperature of 315° C. at a base paper running speed of 200m/minute. In this case, there was used a cooling roll having a surfaceroughness such that the surface of a back layer to be formed had acentral plane average roughness SRa of 1.15 μm. The used cooling rollhad been surface-roughened by a liquid honing method, and was operatedat a cooling water temperature of 12° C.

(Resin composition R1)

A compounded resin composition prepared by pre-melting and pre-mixing 70parts by weight of a high-density polyethylene resin (density 0.967g/cm³, MFR=5 g/10 minutes) and 30 parts by weight of a low-densitypolyethylene resin (density 0.924 g/cm³, MFT=0.6 g/10 minutes) with amelt extruder, which was used in the form of pellets.

The front surface of each of three kinds of the base paper was subjectedto corona discharge treatment, and then, it was coated with a resincomposition for a front resin sheet (1), containing 17 parts by weightof a titanium dioxide pigment master batch (to be abbreviated as “masterbatch (MB-1)” hereinafter) containing 47.5% by weight of a tubularmethod low-density polyethylene resin (density 0.918 g/cm³, MFR=8.5 g/10minutes, melting point 108° C., to be abbreviated as “low-densitypolyethylene resin (R2) hereinafter), 50% by weight of an anatase typetitanium dioxide pigment surface-treated with hydrous aluminum oxide(0.50% by weight, based on titanium dioxide, as an Al₂O₃ content), 2.5%by weight of zinc stearate and 150 ppm oftetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methaneas an antioxidant, 8 parts by weight of a titanium dioxide pigmentmaster batch (to be abbreviated as “master batch (MB-2) hereinafter)containing 46.25% by weight a low-density polyethylene resin (R2), 50%by weight of the above titanium dioxide pigment, 1.25% by weight ofUltramarine (#2000, supplied by Daiichi Kasei Kogyo K.K.), 2.5% byweight of zinc stearate and 150 ppm of the above antioxidant, 57.6 partsby weight of an autoclave method low-density polyethylene resin (density0.920 g/cm³, MFR=4.5 g/10 minutes, melting point 109° C., to beabbreviated as “low-density polyethylene resin (R3) hereinafter) and17.4 parts by weight of a Phillips method high-density polyethyleneresin (density 0.967 g/cm³, MFR=7.0 g/10 minutes, melting point 130° C.,to be abbreviated as “high-density polyethylene resin (R4) hereinafter),by melt extrusion coating with a melt extruder at a resin temperature of315° C. at a base paper running speed of 200 m/minute at a linearpressure of 40 kgf/cm between a mirror-surfaced cooling roll and a pressroll, to form a layer having a thickness of 28 μm. The melt extrusioncoatings of the polyethylene resins on the front surfaces and thereverse surfaces were carried out by a so-called tandem method in whichconsecutive melt extrusion coatings were carried out. In this case, thesurfaces of the resin layers containing the titanium dioxide pigment inthe resin-coated paper were produced as glossy surfaces.

Separately, after subjected to corona discharge treatment, the frontsurface of each of three kinds of the base paper was coated with a frontresin sheet (2) in the same manner as in the formation of the frontresin sheet (1) except that the same resin composition as that used forthe front resin sheet (1), to form a lower layer having a thickness of14 μm, and the same resin composition as that used for the front resinsheet (1), to form an upper layer having a thickness of 14 μm, wereextruded with a two-layer co-extruder by two-layer concurrent extrusioncoating at a resin temperature of 315° C. each at a base paper runningspeed of 200 m/minute at a linear pressure, between a mirror-surfacedcooling roll and a press roll, of 40 kgf/cm.

Separately, further, after subjected to corona discharge treatment, thefront surface of each of three kinds of the base paper was coated with afront resin sheet (3) in the same manner as in the formation of thefront resin sheet (1) except that the same resin composition as thatused for the front resin sheet (1), to form a lower layer having athickness of 14 μm, and the same resin composition as that used for thefront resin sheet (1), to form an upper layer having a thickness of 14μm, were consecutively extruded with extruders by consecutive meltextrusion coating in different stations in the order of the lower layerand then the upper layer at a resin temperature of 315° C. each at abase paper running speed of 200 m/minute at a linear pressure, between amirror-surfaced cooling roll and a press roll, of 40 kgf/cm.

Further, after the front and reverse resin sheets were formed and beforeeach resin-coated paper was taken up, the reverse resin sheet of eachresin-coated paper was subjected to corona discharge treatment, and thenthe following back layer coating liquid was applied on machine. That is,a back layer coating liquid containing colloidal silica:styrene-basedlatex=1:1 and further containing sodium polystyrenesulfonate and aproper amount of a coating aid was applied so as to form a back coatinghaving a sodium polystyrenesulfonate content of 0.021 g/m² as a dryweight and a latex content (as a solid content) of 0.21 g/cm² as a dryweight.

After the back layer was formed and before each resin-coated paper wastaken up, the front resin sheet of each resin-coated paper was subjectedto corona discharge treatment, an undercoating liquid containing 1.2 gof line-treated gelatin, 0.3 g of low-molecular-weight gelatin (P-3226,supplied by Nitta Gelatin K.K.), 0.3 g of a methanol solution containing10% by weight of butyl p-hydroxybenzoic acid and 0.45 g of amethanol/water mixture containing 5% by weight of 2-ethylhexylsulfosuccinate, the total amount of the undercoating liquid beingadjusted to 100 g by adding water, was uniformly applied on machine toform an undercoat having a gelatin application amount of 0.06 g/m².

When the supports for imaging materials were produced, the front resinsheet of each support was evaluated for the property of peeling from acooling roll as follows. When the supports were produced, theirregularity of peeling was visually oversed. Further, the surface stateon the front side of each support was observed through light comingaskew, to visually determine the degree of occurrence of non-uniformityin peeling. The ratings of the evaluations are as follows (the largerthe grade number is, the better the property of peeling is. the smallerthe grade number, the poorer the property of peeling is).

Grades 10-9: The peeling from a cooling roll is completely free ofirregularity, almost no peeling-caused non-uniformity occurs, and theproperty of peeling is excellent.

Grades 8-7: The peeling from a cooling roll is almost free ofirregularity, peeling-caused non-uniformity slightly occurs, and theproperty of peeling is good.

Grades 6-5: The peeling from a cooling roll shows slight irregularity,peeling-caused non-uniformity occurs to some extent, while a support hasno problem in practical use.

Grades 4-1: The peeling from a cooling roll shows irregularity,peeling-caused non-uniformity occurs to a great extent, and a supporthas a problem in practical use.

Then, a photographic print having a support for an imaging material wasevaluated for gloss appearance by the following method.

A blue-sensitive emulsion layer containing a yellow color formingcoupler was formed on the undercoat layer of the support, and anintermediate layer containing a color mixing preventer, agreen-sensitive emulsion layer containing a magenta color formingcoupler, an ultraviolet absorbent layer containing an ultravioletabsorbent, a red-sensitive emulsion layer containing a cyan colorforming coupler and a protective layer were consecutively formed, toobtain a color printing paper having a total gelatin amount of 7 g/m².Each color-sensitive emulsion layer contained silver chlorobromidecorresponding to 0.6 g/m² of silver nitrate, gelatin necessary for theformation, dispersion and film formation of silver halide and theformation of a film, proper amounts of a fogging preventer, asensitizing dye, an application aid, a film curing agent, and athickener and a proper amount of a filter dye.

Then, the above-obtained color printing paper was stored at 35° C. underconstant humidity for 5 days, a group picture (photograph of manypeople) was printed, subjected to development treatments such asdevelopment, bleaching, fixing and stabilization, and then dried toobtain a photographic print. Separately, print samples such as aset-solid white print (not exposed) and a set-solid black print (blackcolor formed) were also prepared. A series of treatments for theexposure, the development and the drying were carried out with anautomatic printer and an automatic developing machine. The colorformation and development procedures were carried out in the order ofcolor formation and development (45 seconds)→bleaching and fixing (45seconds)→stabilization (90 seconds)→drying. The so-obtained photographicprints of the universal photograph, the set-solid white print and theset-solid black print were totally evaluated for gloss appearance by 10people as monitors.

The ratings of evaluation of the gloss appearance are as follows.

⊙: The gloss appearance is very high.

⊙-◯: The gloss appearance is considerably high.

◯: The gloss appearance is far higher.

◯-□: The gloss appearance is high.

□: The gloss appearance is slightly low.

Δ: The gloss appearance is low and there is a problem in practical use.

X: The gloss appearance is very low.

Table 1 shows the results.

TABLE 1 Base paper Upper layer/ lower layer thickness RPy Front resinPeeling Gloss ratio (mV) sheet property appearance CEx. 1 Single layer140 Single layer 5 X CEx. 2 Single layer 140 Co-extrusion 5 Δ CEx. 3Single layer 140 Consecutive 9 Δ extrusion CEx. 4 25/75 135 Single layer5 Δ Ex. 1 25/75 135 Co-extrusion 7 □ Ex. 2 25/75 135 Consecutive 9 ◯-□extrusion CEx. 5 50/50 135 Single layer 5 Δ Ex. 3 50/50 135 Co-extrusion7 ◯-□ Ex. 4 50/50 135 Consecutive 8 ◯ extrusion Ex. = Example, CEx. =Comparative Example

The results in Table 1 show that the supports (Examples 1 to 4) of thepresent invention obtained by making two-layered paper from abroad-leaved tree pulp and coating the surface with a two-layered resinby co-extrusion or consecutive extrusion are excellent supports whichgive photographic prints having high gloss appearance and are excellentin the property of peeling and free of the occurrence of peelingnon-uniformity.

On the other hand, the supports (Comparative Examples 1 to 5) out of thescope of the present invention, of which the base paper, the front resinsheet or both has or have a mono-layered structure, give photographicprints having low gloss appearance, and involve a problem.

EXAMPLES 5-8 AND COMPARATIVE EXAMPLES 6-10

Examples 1 to 4 and Comparative Examples 1 to 5 were repeated exceptthat the broad-leaved tree bleached kraft pulp was replaced with abroad-leaved tree bleached sulfite pulp. Table 2 shows the results.

TABLE 2 Base paper Upper layer/ lower layer thickness RPy Front resinPeeling Gloss ratio (mV) sheet property appearance CEx. 6 Single layer135 Single layer 5 Δ CEx. 7 Single layer 135 Co-extrusion 5 Δ CEx. 8Single layer 135 Consecutive 8 Δ extrusion CEx. 9 25/75 130 Single layer5 Δ Ex. 5 25/75 130 Co-extrusion 7 ◯-□ Ex. 6 25/75 130 Consecutive 8 ◯extrusion CEx. 10 50/50 130 Single layer 5 Δ Ex. 7 50/50 130Co-extrusion 7 ◯-□ Ex. 8 50/50 130 Consecutive 9 ◯ extrusion Ex. =Example, CEx. = Comparative Example

The results in Table 2 show that the supports of which the base paperand the front resin sheet are formed to have a two-layered structure inExamples of the present invention are also excellent supports forimaging materials when a broad-leaved tree bleached sulfite pulp isused.

EXAMPLES 9-12 AND COMPARATIVE EXAMPLES 11-15

Examples 5 to 8 and Comparative Examples 6 to 10 were repeated exceptthat the average fiber length of the broad-leaved bleached sulfite pulpwas changed to 1.0 mm. Table 3 shows the results.

TABLE 3 Base paper Upper layer/ lower layer thickness RPy Front resinPeeling Gloss ratio (mV) sheet property appearance CEx. 11 Single layer170 Single layer 5 X CEx. 12 Single layer 170 Co-extrusion 7 X CEx. 13Single layer 170 Consecutive 9 X extrusion CEx. 14 25/75 168 Singlelayer 6 X Ex. 9 25/75 168 Co-extrusion 7 □ Ex. 10 25/75 168 Consecutive9 □ extrusion CEx. 15 50/50 167 Single layer 6 X Ex. 11 50/50 167Co-extrusion 7 □ Ex. 12 50/50 167 Consecutive 9 □ extrusion Ex. =Example, CEx. = Comparative Example

The results in Table 3 show that the gloss appearance when a pulp havingan average fiber length of 1.0 mm is used is poor as compared with thegloss appearance when a pulp having an average fiber length of 0.6 mm isused, but that the gloss appearance when the base paper and the frontresin sheet are formed to have a two-layered structure each is higherthan the gloss appearance when the base paper or the front resin sheetare not so formed or neither of them are so formed.

EXAMPLES 13-18

Examples 5 and 6 were repeated except that the average fiber length ofthe pulp was changed to 0.4 mm, 0.5 mm or 0.8 mm. Table 4 shows theresults.

Photographic materials were evaluated for stiffness as follows. A 13cm×13 cm color photographic print was evaluated by 10 people asmonitors. The color photographic print was manually held and shaken upand down to evaluate the strength of stiffness on the basis of manualfeeling. The ratings of the evaluation are as follows. ◯: The stiffnessis strong. □: The stiffness is strong to some extent. Δ: The stiffnessis weak to some extent, but a photographic material is acceptable inpractical use. X: The stiffness is weak and there is a problem inpractical use.

TABLE 4 Fiber Gloss length RPy Front resin Peeling appear- (mm) (mV)sheet property ance Stiffness Ex. 13 0.4 110 Co-extrusion 5 ⊚-◯ Δ Ex. 140.5 120 Co-extrusion 6 ◯ □ Ex. 5 0.6 130 Co-extrusion 7 ◯-□ ◯-□ Ex. 150.8 150 Co-extrusion 8 □ ◯ Ex. 16 0.4 110 Consecutive 6 ⊚-◯ Δ extrusionEx. 17 0.5 120 Consecutive 7 ⊚-◯ □ extrusion Ex. 6 0.6 130 Consecutive 8◯ ◯-□ extrusion Ex. 18 0.8 150 Consecutive 9 ◯-□ ◯ extrusion Ex. =Example

The results in Table 4 show that with an increase in the average fiberlength of a pulp, higher gloss appearance is obtained but that thestrength of stiffness decreases.

EXAMPLES 19 TO 27

Example 5 was repeated except that the fiber length of pulp of the upperlayer of the base sheet and the finish thickness of the upper layer werechanged as shown in Table 5. Table 5 shows the results.

TABLE 5 Thickness of Fiber length upper layer of upper of paper layer ofRpy Peeling Gloss (μm) paper (mm) (mV) property appearance Ex. 19 10 0.3123 5 ◯ Ex. 20 10 0.4 125 5 ◯-□ Ex. 21 10 0.5 128 6 ◯-□ Ex. 22 30 0.3115 6 ⊚-◯ Ex. 23 30 0.4 120 7 ◯ Ex. 24 30 0.5 125 7 ◯-□ Ex. 25 50 0.3105 6 ⊚-□ Ex. 26 50 0.4 110 6 ⊚-□ Ex. 27 50 0.5 115 7 ◯ Ex. = Example

The results in Table 5 show the following. When front resin sheets arestructured to have two layers by co-extrusion, the smaller the averagefiber length of pulp of that layer of the base paper which is adjacentto the front resin sheet is, the higher the gloss appearance is. Thegloss appearance when the thickness of the layer adjacent to the frontresin sheet is 30 μm is higher than the gloss appearance when thethickness of the layer adjacent to the front resin sheet is 10 μm, andfurther, the gloss appearance when the thickness of the layer adjacentto the front resin sheet is 50 μm is higher than the gloss appearancewhen the thickness of the layer adjacent to the front resin sheet is 30μm.

EXAMPLES 28-36

Example 6 was repeated except that the fiber length of pulp of the upperlayer of the base sheet and the finish thickness of the upper layer werechanged as shown in Table 6. Table 6 shows the results.

TABLE 6 Thickness of Fiber length upper layer of upper of paper layer ofRpy Peeling Gloss (μm) paper (mm) (mV) property appearance Ex. 28 10 0.3123 6 ⊚-◯ Ex. 29 10 0.4 125 6 ◯ Ex. 30 10 0.5 128 7 ◯ Ex. 31 30 0.3 1157 ⊚-◯ Ex. 32 30 0.4 120 8 ⊚-◯ Ex. 33 30 0.5 125 8 ◯ Ex. 34 50 0.3 105 7⊚ Ex. 35 50 0.4 110 7 ⊚ Ex. 36 50 0.5 115 8 ⊚-◯ Ex. = Example

The results in Table 6 also show the following. When front resin sheetsare structured to have two layers by consecutive extrusion, the smallerthe average fiber length of pulp of that layer of the base paper whichis adjacent to the front resin sheet is, the higher the gloss appearanceis. The gloss appearance when the thickness of the layer adjacent to thefront resin sheet is 30 μm is higher than the gloss appearance when thethickness of the layer adjacent to the front resin sheet is 10 μm, andfurther, the gloss appearance when the thickness of the layer adjacentto the front resin sheet is 50 μm is higher than the gloss appearancewhen the thickness of the layer adjacent to the front resin sheet is 30μm.

EXAMPLES 37-40

Examples 6 was repeated except that the resin temperatures of the resincompositions for the upper layer and the lower layer were set as shownin Table 7 when the front resin sheets (3) were formed by consecutivemelt extrusion coating. Table 7 shows the results.

TABLE 7 Resin temperature (° C.) Peeling Gloss Lower layer Upper layerproperty appearance Example 37 315 315 8 ⊚ Example 38 315 310 9 ⊚Example 39 315 300 10  ⊚ Example 40 310 310 9 ⊚

The results in Table 7 show the following. In the present invention,when the resin compositions for the front resin sheet having amulti-layered structure are extruded for melt extrusion coating, it ispreferred, in view of the effect on improvement in the property ofpeeling, to set the temperature of the resin composition for the uppermost layer at a lower temperature than the temperature of the resincomposition for the resin layer under the uppermost layer.

EXAMPLES 41 TO 45

Example 6 was repeated except that the coating thickness of the upperlayer and the coating thickness of the lower layer of the front resinsheet (3) were changed as shown in Table 8. Table 8 shows the results.

TABLE 8 Coating thickness of resin layer Peeling Gloss Lower layer Upperlayer property appearance Example 41 6 22 6 □ Example 42 7.5 20.5 6 ◯Example 43 11 17 7 ⊚-◯ Example 44 14 14 7 ⊚ Example 45 21 7 8 ⊚-◯

The results in Table 8 show the following. Of the supports for imagingmaterials in the present invention, of which the front resin sheets areconstituted to have a multi-layered structure, in view of the effect onimprovements in the gloss appearance of a photographic print and theproperty of peeling, the thickness of the resin layer composed of atleast the lowermost layer is preferably at least 25%, more preferably atleast 39%, particularly preferably at least 50%, of the total thicknessof the resin layers.

EXAMPLES 46-52

Example 6 was repeated except that the resin composition for the upperlayer and the lower layer was replaced with the following resincompositions (6UA) to (6UD) and (6LE) to (6LG) in a combination shown inTable 9.

Resin compositions for upper layer: (6UA)-(6UD)

Resin composition (6UA): Resin composition containing 17 parts by weightof master batch (MB-1) used in Example 6, 8 parts by weight of masterbatch (MB-2) used in Example 6 and 75 parts by weight a low-densitypolyethylene resin (R3) which was the same as that used in Example 6.

Resin composition (6UB): The same resin composition for an upper layer,as that used in Example 6 (content of high-density polyethylene based onthe total resin components for upper layer: 20.1% by weight).

Resin composition (6UC): Resin composition containing 17 parts by weightof master batch (MB-1), 8 parts by weight of master batch (MB-2), 40.2parts by weight of low-density polyethylene resin (R3) and 34.8 parts byweight (corresponding to 40.1% by weight based on the total resincomponents for upper layer) of high-density polyethylene resin (R4).

Resin composition (6UD): Resin composition containing 21 parts by weightof master batch (MB-1), 9 parts by weight of master batch (MB-2), 53.1parts by weight of low-density polyethylene resin (R3) and 16.9 parts byweight (corresponding to 20.1% by weight based on the total resincomponents for upper layer) of high-density polyethylene resin (R4).

Resin compositions for lower layer: (6LE)-(6LG) Resin composition (6LE):The same composition for a lower layer as that used in Example 6.

Resin composition (6LF): Autoclave-method low-density polyethylene resinhaving a density of 0.924 g/cm³, an MFR of 4.5 g/10 minutes and amelting point of 111° C.

Resin composition (6LG): Tubular-method low-density polyethylene resinhaving a density of 0.924 g/cm³, an MFR of 3.0 g/10 minutes and amelting point of 111° C.

Table 9 shows the results.

TABLE 9 Resin compositions Peeling Gloss Lower layer Upper layerProperty appearance Example 46 (6LE) (6UA) 8 ⊚-◯ Example 47 (6LE) (6UB)9 ⊚ Example 48 (6LE) (6UC) 10  ⊚ Example 49 (6LE) (6UD) 9 ⊚ Example 50(6LF) (6UD) 9 ⊚ Example 51 (6LG) (6UD) 9 ⊚ Example 52 (6LG) (6UB) 9 ⊚

The results in Table 9 show the following. Of the supports for imagingmaterials in the present invention, of which the front resin sheet isconstituted to have a multi-layered structure by consecutive extrusion,the support having the uppermost layer containing at least one resinhaving a higher density or melting point than the resin of the resinlayer under it is preferred in view of the effect on improvements in thegloss appearance of a photographic print and the property of peeling.Further, even if the contents of additives such as a titanium dioxidepigment, a colorant pigment, a releasing agent and an antioxidant in thelayer below the uppermost layer are smaller than the contents thereof inthe uppermost layer, it does not affect the effects of the presentinvention and is advantageous in economic performance.

EXAMPLES 53-59

Example 5 was repeated except that the resin composition for the upperlayer and the lower layer was replaced with the following resincompositions (5UA) to (5UD) and (5LE) to (5LG) in a combination shown inTable 10. The (5UA) to (5UD) and (5LE) to (5LG) were substantially thesame as the (6UA) to (6UD) and (6LE) to (6LG) except that theconsecutive extrusion was replaced with co-extrusion. Table 10 shows theresults.

TABLE 10 Resin compositions Peeling Gloss Lower layer Upper layerProperty appearance Example 53 (5LE) (5UA) 5 □-Δ Example 54 (5LE) (5UB)6 ◯-□ Example 55 (5LE) (5UC) 7 ⊚-◯ Example 56 (5LE) (5UD) 6 ◯ Example 57(5LF) (5UD) 6 ◯-□ Example 58 (5LG) (5UD) 6 ◯-□ Example 59 (5LG) (5UB) 6◯-□

The results in Table 10 show the following. Even when the front resinsheet is formed by co-extrusion in the support for an imaging material,of which the front resin sheet is constituted to have a multi-layeredstructure, the support having the uppermost layer containing at leastone resin having a higher density or melting point than the resin of theresin layer under it is preferred in view of the effect on improvementsin the gloss appearance of a photographic print and the property ofpeeling. Further, even if the contents of additives such as a titaniumdioxide pigment, a colorant pigment, a releasing agent and anantioxidant in the layer below the uppermost layer are smaller than thecontents thereof in the uppermost layer, it does not affect the effectsof the present invention and is advantageous in economic performance.

EXAMPLES 60-62

Example 5 was repeated except that the resin composition for the upperlayer and the lower layer of the front resin sheet (2) was replaced withthe resin composition (5UD), that the resin composition of the lowerlayer was replaced with the resin composition (5LF) and that the runningspeed of the base paper was set as shown in Table 11. Table 11 shows theresults.

EXAMPLES 63-65

Example 50 was repeated except that the running speed of the base paperwas set as shown in Table 11. Table 11 shows the results.

TABLE 11 Running speed of base paper Peeling Gloss (m/minute) propertyappearance Example 60 200 7 ◯-□ Example 61 250 6 □ Example 62 300 5 ΔExample 63 200 9 ⊚ Example 64 250 8 ⊚ Example 65 300 7 ⊚

The results in Table 11, i.e., the comparison between Example 60 andExample 63 (the running speed of the base paper was 200 m/minute), thecomparison between Example 61 and Example 64 (the running speed of thebase paper was 250 m/minute), and the comparison between Example 62 andExample 65 (the running speed of the base paper was 300 m/minute) showthe following. With an increase in the running speed of the base paper(i.e., with an increase in the speed of production of the support for animaging material), that is, when the running speed of the base paper isat least 200 m/minute, further, at least 250 m/minute, particularly, atleast 300 m/minute, of the supports of the present invention, thesupport of which the front resin sheet is constituted to have amulti-layered structure by a consecutive melt extrusion coating methodis particularly preferred in view of the effects on improvements in thegloss appearance of a photographic print and the property of peeling.Further, the above support for an imaging material can give an imagingmaterial and a print thereon which have a high gloss appearance, and itis an excellent support for an imaging material, which support is freefrom the occurrence of peeling non-uniformity and can be stably producedat a high speed.

EXAMPLE 66

The following ink receiving layer was formed on the support obtained inExample 6 in place of the multi-layered silver halide color photographconstituting layer, to prepare an inkjet recording material. As aresult, the inkjet recording material had a high-gloss appearance andwas free of non-uniformity in gloss, and the above support was thereforeexcellent.

The ink receiving layer was formed by applying a coating solutioncontaining 30 g of an aqueous solution containing 10% by weight of analkali-treated gelatin having a molecular weight of 70,000, 37.5 g of anaqueous solution containing 8% by weight of sodium carboxymethylcellulose (etherification degree 0.7-0.8, viscosity of 2 wt% aqueoussolution measured with Brookfield viscometer 5 cp or less), 0.3 g of amethanol solution containing 5% by weight of an epoxy compound (NER-010,supplied by Nagase Sangyo K.K.), 0.5 g of a methanol/water mixturecontaining 5% by weight of 2-ethylhexyl sulfosuccinate and 31.7 g ofpurified water, and the ink receiving layer had a solid content of 7g/cm².

EXAMPLES 67-73 AND COMPARATIVE EXAMPLES 16-23

A broad-leaved tree bleached pulp was adjusted to a concentration of 4%by weight in terms of an absolute dry weight and beaten so as to have anaverage fiber length of 0.4 mm and a Canadian Standard freeness of 350ml. The obtained pulp was used as a pulp for an upper layer (layeradjacent to a resin sheet on a side where an image is to be formed) of athree-layered paper. Similarly, a broad-leaved tree bleached sulfitepulp was beaten to have an average fiber length of 0.8 mm and a Canadianstandard freeness of 350 mm, and the obtained pulp was used as a pulpfor an intermediate layer. Further, a pulp mixture containing 90% byweight of a broad-leaved tree kraft pulp and 10% by weight of abroad-leaved tree sulfite pulp was beaten to have an average fiberlength of 0.6 mm and a Canadian standard freeness of 350 mm, and theobtained pulp was used as a pulp for a lower layer. After the beating, 3parts by weight of cationized starch, 0.2 part by weight of anionizedpolyacrylamide, 0.4 part by weight (as a ketene dimer content) of analkylketene dimer emulsion, 0.4 part by weight of a polyamideepichlorohydrin resin and proper amounts of a fluorescent brightener, ablue dye and a red dye were added to 100 parts by weight of each pulp toprepare paper material slurries. Then, the paper material slurries wereplaced on a Fourdriner paper machine running at a speed of 200 m/minuteto form three layers (partly, two layers) at varied levels of an upper,intermediate and lower layer balance as shown in Table 12, and a web wasformed with applying proper turbulence. In a wet part, the web wassubjected to three-stage wet press at a linear pressure adjusted in therange of 15 to 100 kgf/cm. Then, the web was treated with a smoothingroll. In a subsequent drying part, the web was subjected to two-stagebulk density increasing press at a linear pressure adjusted in the rangeof 30 to 70 kgf/cm and then dried. Then, during the drying, a size presssolution containing 4 parts by weight of carboxy-modified polyvinylalcohol, 0.05 part by weight of a fluorescent brightener, 0.002 part byweight of a blue dye, 4 parts by weight of sodium chloride and 92 partsby weight of water was size-pressed at a speed of 25 g/cm², and the webwas dried such that the base paper to be finally obtained had a watercontent of 8% by weight in terms of an absolute dry water content. Theweb was machine-calendered at a linear pressure of 70 kgf/cm to obtain abase paper for a support for an imaging material, the base paper havinga basis weight of 170 g/m², a density of 1.04 g/cm³ and a film thicknessnon-uniformity index Rpy as shown in Table 12.

A base paper for an imaging material was prepared in the same manner asin Example 72 except that the paper material slurry for an upper layerand the paper material slurry for a lower layer in Example 72 were mixedin the a mixing ratio which was the same as the ratio of these slurriesin Example 72. The obtained base paper was used as a base paper inComparative Example 23.

The surface (reverse surface) of each base paper, opposite to thesurface where an image-forming layer was to be formed, was subjected tocorona discharge treatment, and then, the following resin composition(R1) was coated on the reverse surface of each base paper to form aresin layer having a thickness of 20 μm by melt extrusion coating at aresin temperature of 315° C. at a base paper running speed of 200m/minute. In this case, there was used a cooling roll having a surfaceroughness such that the surface of a back layer to be formed had acentral plane average roughness SRa of 1.15 μm. The used cooling rollhad been surface-roughened by a liquid honing method, and was operatedat a cooling water temperature of 12° C.

(Resin composition R1)

A compounded resin composition prepared by pre-melting and pre-mixing 70parts by weight of a high-density polyethylene resin (density 0.967g/cm³, MFR=5 g/10 minutes) and 30 parts by weight of a low-densitypolyethylene resin (density 0.924 g/cm³, MFT=0.6 g/10 minutes) with amelt extruder, which was used in the form of pellets.

The front surface of the base paper was subjected to corona dischargetreatment, and then, it was coated with a resin composition for a frontresin sheet (1), containing 17 parts by weight of the same titaniumdioxide pigment master batch as the master batch (MB-1) used in Examples1 to 4, 8 parts by weight of the same titanium dioxide pigment masterbatch as the master batch (MB-2) used in Examples 1 to 4, 57.6 parts byweight of the same autoclave-method low-density polythylene resin as thelow-density polyethylene resin (R3) used in Examples 1 to 3 and 17.4parts by weight of the same Phillips method high-density polyethyleneresin as the high-density polyethylene resin (R4) used in Examples 1 to4, by melt extrusion coating with a melt extruder at a resin temperatureof 315° C. at a base paper running speed of 200 m/minute at a linearpressure of 40 kgf/cm between a mirror-surfaced cooling roll and a pressroll, to form a layer having a thickness of 28 μm. The melt extrusioncoatings of the polyethylene resins on the front surface and the reversesurface were carried out by a so-called tandem method in whichconsecutive melt extrusion coatings were carried out. In this case, thesurface of the resin layer containing the titanium dioxide pigment inthe resin-coated paper was produced as a glossy surface.

Further, after the front and reverse resin sheets were formed and beforethe resin-coated paper was taken up, the reverse resin sheet of theresin-coated paper was subjected to corona discharge treatment, and thenthe following back layer coating liquid was applied on machine. That is,a back layer coating liquid containing colloidal silica:styrene-basedlatex=1:1 and further containing sodium polystyrenesulfonate and aproper amount of a coating aid was applied so as to form a back layerhaving a sodium polystyrenesulfonate content of 0.021 g/m² as a dryweight and a latex content (as a solid content) of 0.21 g/cm² as a dryweight.

After the back layer was formed and before the resin-coated paper wastaken up, the front resin sheet of the resin-coated paper was subjectedto corona discharge treatment, an undercoating liquid containing 1.2 gof lime-treated gelatin, 0.3 g of low-molecular-weight gelatin (P-3226,supplied by Nitta Gelatin K.K.), 0.3 g of a methanol solution containing10% by weight of butyl p-hydroxybenzoic acid and 0.45 g of amethanol/water mixture containing 5% by weight of 2-ethylhexylsulfosuccinate, the total amount of the undercoating liquid beingadjusted to 100 g by adding water, was uniformly applied on machine toform an undercoat having a gelatin application amount of 0.06 g/m².

A photographic print having the support for an imaging material wasevaluated in the same manner as in Examples 1 to 4 and comparativeExamples 1˜5.

For the evaluation of stiffness, an imaging material was evaluated forstiffness as follows. A 13 cm×18 cm color photographic print wasevaluated by 10 people as monitors. The color photographic print wasmanually held and shaken up and down to evaluate the strength ofstiffness on the basis of manual feeling.

The ratings of the evaluation are as follows.

⊙: The stiffness is very strong.

◯: The stiffness is strong.

□: The stiffness is weak to some extent, but an imaging material isacceptable in practical use.

X: The stiffness is weak and floppy, and there is a problem in practicaluse.

Table 12 shows the results.

TABLE 12 Structure of base paper [Thickness ratio (%)] Inter- GlossUpper mediate Lower Rpy appear- layer layer layer (mV) Stiffness anceCEx. 16  5 35 60 138 ◯ X CEx. 17  5 25 70 135 ◯ X CEx. 18 10 40 50 133 XΔ CEx. 19 20 30 50 129 X □ CEx. 20 30 20 50 120 X ◯ CEx. 21 40 10 50  97X ◯ CEx. 22 50 — 50  96 X ◯ Ex. 67 10 30 60 131 ◯ □ Ex. 68 10 20 70 128◯ □-◯ Ex. 69 20 20 60 125 □ ◯ Ex. 70 20 10 70 123 ◯ ◯ Ex. 71 30 10 60115 □ ◯ Ex. 72 30 — 70 112 ◯ ◯ Ex. 73 40 — 60 108 □ ⊚ CEx. 23 Singlelayer of mixture of 141 ◯ X compositions used for upper and lower layersin Example 72

The results in Table 12 show the following. The photographic printshaving the base paper having a smaller content of a short fiber pulp inComparative Examples 16 and 17 exhibit insufficient gloss appearance. Onthe other hand, the photographic prints having the base paper of whichthe lower layer has a smaller thickness exhibit insufficient stiffness.In contrast, the photographic prints in Examples 67 to 73 of the presentinvention are well-balanced between the gloss appearance and thestiffness. Further, the photographic print in Comparative Example 23,which has the single-layered base paper formed of a mixture of the pulpsfor the upper and lower layers in Example 72, exhibits insufficientgloss appearance.

EXAMPLES 74-85

Example 71 was repeated except that the fiber length of the pulp for theupper layer and the thickness of the upper layer were changed as shownin Table 13. Table 13 shows the results.

TABLE 13 Fiber Structure of base paper length of [Thickness ratio (%)]of pulp Inter- gloss for upper Upper mediate Lower Rpy Stiff- appear-layer layer layer layer (mV) ness ance Ex. 74 0.3 mm 10 30 60 132 ◯ ◯Ex. 75 ″ 20 20 ″ 123 □-◯ ◯-⊚ Ex. 76 ″ 30 10 ″ 114 □-◯ ⊚ Ex. 77 ″ 40 — ″105 □ ⊚ Ex. 78 0.4 mm 10 30 ″ 131 ◯ □ Ex. 79 ″ 20 20 ″ 127 ◯ ◯ Ex. 80 ″30 10 ″ 117 ◯ ◯ Ex. 81 ″ 40 — ″ 110 □ ⊚ Ex. 82 0.5 mm 10 30 ″ 138 ◯ □Ex. 83 ″ 20 20 ″ 130 ◯ ◯ Ex. 84 ″ 30 10 ″ 122 ◯ ◯ Ex. 85 ″ 40 — ″ 115□-◯ ◯ Ex. = Example

Table 13 shows the following. The smaller the average fiber length is,the higher the gloss appearance is, and the larger the average fiberlength is, the higher the stiffness is. The larger the thickness of theupper layer is, the higher the gloss appearance is, and the smaller thethickness of the upper layer is, the higher the stiffness is. When thethickness of the upper layer is in the range of 20 to 30% within thescope of the present invention, the gloss appearance and the stiffnessare particularly well-balanced.

EXAMPLES 86-97

Example 71 was repeated except that the fiber length of the pulp for thelower layer and the thickness of the lower layer were changed as shownin Table 14. Table 14 shows the results.

TABLE 14 Pulp for lower layer Broad- Structure of base paper leaved[Thickness ratio (%)] tree Inter- kraft Upper mediate Lower Fiber pulpRpy Gloss- layer layer layer length (wt %) (mV) Stiffness appearanceEx.86 30 10 60 0.5 mm  80 115 □ ◯ Ex.87 ″ — 70 ″ ″ 114 □ ◯ Ex.88 ″ 10 600.65 mm ″ 117 □ ◯ Ex.89 ″ — 70 ″ ″ 115 ◯ ◯ Ex.90 ″ 10 60 0.8 mm ″ 119 ◯◯ Ex.91 ″ — 70 ″ ″ 118 ◯ ◯ Ex.92 ″ 10 60 0.5 mm 100 114 □ ◯ Ex.93 ″ — 70″ ″ 118 ◯ ◯ Ex.94 ″ 10 60 0.65 mm ″ 115 ◯ ◯ Ex.95 ″ — 70 ″ ″ 113 ◯ ◯Ex.96 ″ 10 60 0.8 mm ″ 118 ◯ ◯ Ex.97 ″ — 70 ″ ″ 116 ◯ ◯

Table 14 shows that the larger the fiber length of the lower layer is,the more advantageous the larger fiber length is for the stiffness, andthat when the fiber length of the lower layer is in the above range,there is no particular problem on the gloss appearance.

EXAMPLES 98-100

Example 72 was repeated except that the average fiber length of thepulps for the upper and lower layers, the content of the broad-leavedtree kraft pulp in the pulp for the lower layer, the kinds of the pulpsfor the upper layer and the kinds of the rest of the pulps for the lowerlayer were as shown in Table 15. Table 15 shows the results.

TABLE 15 Pulp constitution Lower layer The Upper layer LK Rest GlossFiber Fiber (wt of Rpy Stiff- appear- length kind length %) pulp (mV)ness ance Ex. 72 0.4 mm LK 0.6 mm 90 LS 114 ◯ ◯ CEx. 24 0.6 mm LK 0.6 mm90 LS 135 ⊙ X CEx. 25 0.2 mm LK 0.6 mm 90 LS 100 X ⊙ CEx. 26 0.4 mm LK0.6 mm 70 LS 112 X ◯ Ex. 98 0.4 mm LK 0.6 mm 80 LS 113 ◯ ◯ CEx. 27 0.4mm LK 0.45 mm  90 LS 111 X ◯-⊙ CEx. 28 0.4 mm LK 0.9 mm 90 LS 125 ⊙ XCEx. 29 0.4 mm LS 0.6 mm 90 LS 109 X ◯ CEx. 30 0.4 mm NS 0.6 mm 90 LS125 ⊙ Δ CEx. 31 0.4 mm NK 0.6 mm 90 LS 129 ⊙ X CEx. 32 0.4 mm LK 0.6 mm70 NS 125 ⊙ Δ CEx. 33 0.4 mm LK 0.6 mm 70 NK 130 ⊙ X Ex. 99 0.4 mm LK0.6 mm 90 NS 118 ⊙ ◯ Ex. 100 0.4 mm LK 0.6 mm 90 NK 120 ⊙ ◯ Ex. =Example, CEx. = Comparative Example

In Table 15, LK stands for broad-leaved tree kradt pulp, LS stands forbroad-leaved tree sulfite pulp, NK stands for conifer kraft pulp, and NSstands for conifer sulfite pulp. “The rest of pulp” stands for pulpother than broad-leaved tree kraft pulp in the pulp for a lower layer.

Table 15 shows the following. In Comparative Example 24 in which theaverage fiber length of the pulp in the upper layer is large andComparative Examples 30 and 31 in which the conifer pulp is used in theupper layer, the gloss appearance is insufficient. In ComparativeExample 25 in which the average fiber length of the pulp in the upperlayer is small and Comparative Example 29 in which the pulp in the upperlayer is a broad-leaved sulfite pulp, the stiffness is insufficient. Onthe other hand, in Comparative Example in which the content of thebroad-leaved kraft pulp in the lower layer is small and ComparativeExample 27 in which the average fiber length of the pulp in the lowerlayer is small, the stiffness is insufficient. In Comparative Example 28in which the average fiber length of the pulp in the lower layer is toolarge, the gloss appearance is insufficient. In Comparative Examples 32and 33 in which the content of the broad-leaved kraft pulp in the lowerlayer is small but the rest of the pulp is a conifer pulp, the stiffnessis high, while the gloss appearance is insufficient. In contrast, inExamples 98, 99 and 100 of the present invention, the gloss appearanceand the stiffness are both satisfactory.

EXAMPLES 101 AND 102

In Example 101, Example 71 was repeated except that the intermediatelayer was arranged to be positioned between two equal divisions of thelower layer to make a four-layered paper. In Example 102, Example 70 wasrepeated except that the pulp for the intermediate layer and the pulpfor the lower layer were mixed in the same amount ratio to make atwo-layered paper. Table 16 shows the results.

TABLE 16 Clark Gloss Structure of base paper [Thickness Rpy stiff-appear- ratio (%)] (mV) ness ance Ex. Upper Intermediate layer Lower 115◯ ◯ 71 layer 10 layer 30 60 Ex. Upper Lower Inter- Lower 112 □ ◯ 101layer layer 1 mediate layer 2 30 30 layer 30 10 Ex. Upper Intermediatelayer Lower 123 ◯ ◯ 70 layer 10 layer 20 70 Ex. Upper Lower layer 80 112⊙ ◯ 102 layer Mixture of pulps for inter- 20 mediate layer and lowerlayer in Example 70 Ex. = Example

Table 16 shows the following. In Example 101 in which the layers havingan average fiber length of 0.6 mm and containing 90% by weight of abroad-leaved tree kraft pulp does not constitute a continuous layerwhose thickness is 60%, the discontinued layers are disadvantageous forthe stiffness. In Example 102 in which the base paper is composed ofonly two layers, i.e., an upper layer composed of a broad-leaved treekraft pulp having an average fiber length of 0.4 mm and a lower layercomposed of a pulp composition having an average fiber length of 0.6 mmand containing at least 80% by weight of a broad-leaved tree kraft pulp,the base paper is advantageous for the stiffness although the pulpcomposition is the same as that in Example 70.

EXAMPLES 103 AND 104

In Example 103, Example 102 was repeated except that, after the coronadischarge treatment of the front surface of the base paper, the abovefront surface was coated with a front resin sheet (2) in the same manneras in the formation of the front resin sheet (1) except that the sameresin composition as that used for the front resin sheet (1), to form alower resin layer having a thickness of 14 μm, and the same resincomposition as that used for the front resin sheet (1), to form an upperresin layer having a thickness of 14 μm, were extruded with a two-layerco-extruder by two-layer concurrent extrusion coating at a resintemperature of 315° C. each at a base paper running speed of 200m/minute at a linear pressure, between a mirror-surfaced cooling rolland a press roll, of 40 kgf/cm.

In Example 104, Example 102 was repeated except that, after the coronadischarge treatment of the front surface of the base paper, the abovefront surface was coated with a front resin sheet (3) in the same manneras in the formation of the front resin sheet (1) except that the sameresin composition as that used for the front resin sheet (1), to form alower layer having a thickness of 14 μm, and the same resin compositionas that used for the front resin sheet (1), to form an upper layerhaving a thickness of 14 μm, were consecutively extruded with extrudersby consecutive melt extrusion coating in different stations in the orderof the lower layer and then the upper layer at a resin temperature of315° C. each at a base paper running speed of 200 m/minute at a linearpressure, between a mirror-surfaced cooling roll and a press roll, of 40kgf/cm.

The supports for imaging materials were evaluated for the property ofpeeling from the cooling roll at their production time in the samemanner as in Examples 1 to 4.

Table 17 shows the results.

TABLE 17 Peeling Gloss Resin Sheet property appearance Example 102Single layer 6 ◯ Example 103 Co-extrusion 7 ◯-⊚ Example 104 Consecutiveextrusion 10  ⊚

The results in Table 17 show that when the resin sheet has a two-layeredstructure, and further, when it has a two-layered structure produced byconsecutive extrusion, the imaging materials are excellent both in thepeeling property and the gloss appearance.

EXAMPLES 105-108

Example 104 was repeated except that the temperatures of the resincompositions for the upper and lower layers were set as shown in Table18 when the front resin sheet (3) was formed by consecutive meltextrusion coating. Table 18 shows the results.

TABLE 18 Resin temperature (° C.) Peeling Gloss Lower layer Upper layerproperty appearance Example 105 315 315 8 ⊚ Example 106 315 310 9 ⊚Example 107 315 300 10  ⊚ Example 108 310 310 9 ⊚

The results in Table 18 show the following. In the present invention,when the resin compositions for the front resin sheet having amulti-layered structure are extruded for melt extrusion coating, it ispreferred, in view of the effect on improvement in the property ofpeeling, to set the temperature of the resin composition for the uppermost layer at a lower temperature than the temperature of the resincomposition for the resin layer under the uppermost layer.

EXAMPLES 109-113

Example 104 was repeated except that the coating thickness of the upperlayer and the coating thickness of the lower layer of the front resinsheet (3) were changed as shown in Table 19. Table 19 shows the results.

TABLE 19 Coating thickness of resin layer Peeling Gloss Lower layerUpper layer property appearance Example 109 6 22 6 □ Example 110 7.520.5 6 ◯ Example 111 11 17 7 ⊚-◯ Example 112 14 14 7 ⊚ Example 113 21 78 ⊚-◯

The results in Table 19 show the following. Of the supports for imagingmaterials in the present invention, of which the front resin sheets areconstituted to have a multi-layered structure, in view of the effect onimprovements in the gloss appearance of a photographic print and theproperty of peeling, the thickness of the resin layer composed of atleast the lowermost layer is preferably at least 25%, more preferably atleast 39%, particularly preferably at least 50%, of the total thicknessof the resin layers.

EXAMPLES 114-120

Example 104 was repeated except that the resin composition for the upperlayer or the lower layer of the front resin sheet was replaced with thefollowing resin compositions (104UA) to (104UD) and (104LE) to (104LG)in a combination shown in Table 20.

Resin compositions for upper layer: (104UA)-(104UD)

Resin composition (104UA): Resin composition containing 17 parts byweight of master batch (MB-1) used in Example 6, 8 parts by weight ofmaster batch (MB-2) used in Example 6 and 75 parts by weight alow-density polyethylene resin (R3) which was the same as that used inExample 6.

Resin composition (104UB): The same resin composition for an upperlayer, as that used in Example 104 (content of high-density polyethylenebased on the total resin components for upper layer: 20.1% by weight).

Resin composition (104UC): Resin composition containing 17 parts byweight of master batch (MB-1), 8 parts by weight of master batch (MB-2),40.2 parts by weight of low-density polyethylene resin (R3) and 34.8parts by weight (corresponding to 40.1% by weight based on the totalresin components for upper layer) of high-density polyethylene resin(R4).

Resin composition (104UD): Resin composition containing 21 parts byweight of master batch (MB-1), 9 parts by weight of master batch (MB-2),53.1 parts by weight of low-density polyethylene resin (R3) and 16.9parts by weight (corresponding to 20.1% by weight based on the totalresin components for upper layer) of high-density polyethylene resin(R4).

Resin compositions for lower layer: (104LE)-(104LG)

Resin composition (104LE): The same composition for a lower layer asthat used in Example 104.

Resin composition (104LF): Autoclave-method low-density polyethyleneresin having a density of 0.924 g/cm³, an MFR of 4.5 g/10 minutes and amelting point of 111° C.

Resin composition (104LG): Tubular-method low-density polyethylene resinhaving a density of 0.924 g/cm³, an MFR of 3.0 g/10 minutes and amelting point of 111° C.

Table 20 shows the results.

TABLE 20 Resin compositions Peeling Gloss Lower layer Upper layerProperty appearance Example 114 (104LE) (104UA) 8 ⊚-◯ Example 115(104LE) (104UB) 9 ⊚ Example 116 (104LE) (104UC) 10  ⊚ Example 117(104LE) (104UD) 9 ⊚ Example 118 (104LF) (104UD) 9 ⊚ Example 119 (104LG)(104UD) 9 ⊚ Example 120 (104LG) (104UB) 9 ⊚

The results in Table 20 show the following. Of the supports for imagingmaterials in the present invention, of which the front resin sheet isconstituted to have a multi-layered structure by consecutive extrusion,the support having the uppermost layer containing at least one resinhaving a higher density or melting point than the resin of the resinlayer under it is preferred in view of the effect on improvements in thegloss appearance of a photographic print and the property of peeling.Further, even if the contents of additives such as a titanium dioxidepigment, a colorant pigment, a releasing agent and an antioxidant in thelayer below the uppermost layer are smaller than the contents thereof inthe uppermost layer, it does not affect the effects of the presentinvention and is advantageous in economic performance.

EXAMPLES 121-127

Example 103 was repeated except that the resin composition for the upperlayer or the lower layer was replaced with the following resincompositions (103UA) to (103UD) and (103LE) to (103LG) in a combinationshown in Table 21. The (103UA) to (103UD) and (103LE) to (103LG) weresubstantially the same as the (104UA) to (104UD) and (104LE) to (104LG)except that the consecutive extrusion was replaced with co-extrusion.Table 21 shows the results.

TABLE 21 Resin compositions Peeling Gloss Lower layer Upper layerProperty appearance Example 121 (103LE) (103UA) 5 □-Δ Example 122(103LE) (103UB) 6 ◯-□ Example 123 (103LE) (103UC) 7 ⊚-◯ Example 124(103LE) (103UD) 6 ◯ Example 125 (103LF) (103UD) 6 ◯-□ Example 126(103LG) (103UD) 6 ◯-□ Example 127 (103LG) (103UB) 6 ◯-□

The results in Table 21 show the following. Even when the front resinsheet is formed by co-extrusion in the support for an imaging material,of which the front resin sheet is constituted to have a multi-layeredstructure, the support having the uppermost layer containing at leastone resin having a higher density or melting point than the resin of theresin layer under it is preferred in view of the effect on improvementsin the gloss appearance of a photographic print and the property ofpeeling. Further, even if the contents of additives such as a titaniumdioxide pigment, a colorant pigment, a releasing agent and anantioxidant in the layer below the uppermost layer are smaller than thecontents thereof in the uppermost layer, it does not at all affect theeffects of the present invention and is advantageous in economicperformance.

EXAMPLES 128-130

Example 103 was repeated except that the resin composition for the upperlayer and the lower layer of the front resin sheet (2) was replaced withthe resin composition (103UD), that the resin composition of the lowerlayer was replaced with the resin composition (103LF) and that therunning speed of the base paper was set as shown in Table 22. Table 22shows the results.

EXAMPLES 131-133

Example 118 was repeated except that the running speed of the base paperwas set as shown in Table 22. Table 22 shows the results.

TABLE 22 Running speed of base paper Peeling Gloss (m/minute) propertyappearance Example 128 200 7 ◯-□ Example 129 250 6 □ Example 130 300 5 ΔExample 131 200 9 ⊚ Example 132 250 8 ⊚ Example 133 300 7 ⊚

The results in Table 22, i.e., the comparison between Example 128 andExample 131 (the running speed of the base paper was 200 m/minute), thecomparison between Example 129 and Example 132 (the running speed of thebase paper was 250 m/minute), and the comparison between Example 130 andExample 133 (the running speed of the base paper was 300 m/minute) showthe following. With an increase in the running speed of the base paper(i.e., with an increase in the speed of production of the support for animaging material), that is, when the running speed of the base paper isat least 200 m/minute, further, at least 250 m/minute, particularly, atleast 300 m/minute, of the supports of the present invention, thesupport of which the front resin sheet is constituted to have amulti-layered structure by a consecutive melt extrusion coating methodis particularly preferred in view of the effects on improvements in thegloss appearance of a photographic print and the property of peeling.Further, the above support for an imaging material can give an imagingmaterial and a print thereon which have a high gloss appearance, and itis an excellent support for an imaging material, which support is freefrom the occurrence of peeling non-uniformity and can be stably producedat a high speed.

EXAMPLE 134

The following ink receiving layer was formed on the support obtained inExample 104 in place of the multi-layered silver halide color photographconstituting layer, to prepare an inkjet recording material. As aresult, the inkjet recording material had a high-gloss appearance andwas free of non-uniformity in gloss, and the above support was thereforeexcellent.

The ink receiving layer was formed by applying a coating solutioncontaining 30 g of an aqueous solution containing 10%, by weight of analkali-treated gelatin having a molecular weight of 70,000, 37.5 g of anaqueous solution containing 8% by weight of sodium carboxymethylcellulose (etherification degree 0.7-0.8, viscosity of 2 wt % aqueoussolution measured with Brookfield viscometer 5 cp or less), 0.3 g of amethanol solution containing 5% by weight of an epoxy compound (NER-010,supplied by Nagase Sangyo K.K.), 0.5 g of a methanol/water mixturecontaining 5% by weight of 2-ethylhexyl sulfosuccinate and 31.7 g ofpurified water, and the ink receiving layer had a solid content of 7g/cm².

EXAMPLES 135-140 AND COMPARATIVE EXAMPLES 34-37

A broad-leaved bleached kraft pulp was beaten so as to have a fiberlength of 0.56 mm, 0.62 mm or 0.68 mm (in terms of JAPAN TAPPI PaperPulp Testing Method No. 52-89, “Method of testing paper and pulp forfiber length”). Then, to 100 parts by weight of the beaten pulp wereadded 3 parts by weight of cationized starch, 0.2 part by weight ofanionized polyacrylamide, 0.4 part by weight (as a ketene dimer content)of an alkylketene dimer emulsion, 0.4 part by weight of a polyamideepichlorohydrin resin, 1.5 parts by weight of an amphotericpolyacrylamide and proper amounts of a fluorescent brightener, a bluedye and a red dye, to prepare paper material slurries. Then, the papermaterial slurries were placed on a Fourdriner paper machine running at aspeed of 200 m/minute to form a web with applying proper turbulence. Ina wet part, the web was subjected to three-stage wet press at a linearpressure adjusted in the range of 15 to 100 kgf/cm. Then, the web wastreated with a smoothing roll. In a subsequent drying part, the web wassubjected to twp-stage bulk density increasing press at a linearpressure adjusted in the range of 30 to 70 kgf/cm and then dried. Then,during the drying, a size press solution containing 4 parts by weight ofcarboxy-modified polyvinyl alcohol, 0.05 part by weight of a fluorescentbrightener, 0.002 part by weight of a blue dye, 4 parts by weight ofsodium chloride and 92 parts by weight of water was size-pressed at aspeed of 25 g/cm², and the web was dried such that the base paper to befinally obtained had a water content of 8% by weight in terms of anabsolute dry water content. The web was machine-calendered at a linearpressure of 70 to 100 kgf/cm to obtain a base paper for a support for animaging material, the base paper having a basis weight of 170 g/m². Inaddition, the base paper from the pulp having a fiber length of 0.56 mmhad a density of 1.08 g/cm³ and a central plane average roughness SRa of1.20 μm, the base paper from the pulp having a fiber length of 0.62 mmhad a density of 1.05 g/cm³ and a central plane average roughness SRa of1.37 μm, and the base paper from the pulp having a fiber length of 0.68mm had a density of 1.02 g/cm³ and a central plane average roughness SRaof 1.55 μm.

Then, the base paper surface (reverse surface) opposite to the surfacewhere an image-forming layer was to be formed was subjected to coronadischarge treatment, and then, a compounded resin composition containing30 parts by weight of a low-density polyethylene resin (density 0.924g/cm³, MFR=1 g/10 minutes) and 70 parts by weight of a high-densitypolyethylene resin (density 0.967 g/cm³, MFR=15 g/10 minutes) was coatedon the reverse surface to form a resin layer having a thickness of 25 μmwith a melt extrusion applicator at a resin temperature of 320° C. at abase paper running speed of 200 m/minute at a linear pressure of 40kgf/cm in a cooling roll and a press roll.

In this case, the used cooling roll had been surface-roughened by aliquid honing method, and was operated at a cooling water temperature of12° C. Thereafter, a front resin sheet was formed as follows, to producea resin-coated paper.

The base paper surface (front surface) where a silver halide photographconstituting layer was to be formed was subjected to corona dischargetreatment. Then, the following compounded composition (BL-1) or (BL-3)as a composition for a lower layer and the following compoundedcomposition (BL-1), (BL-2), (BL-3), (BL-4) or (BL-5) as a compositionfor an upper layer were coated on the above surface in a combination asshown in Table 23 by two-layer co-extrusion coating with a two-layerco-extruder at a resin temperature of 315° C. at a base paper runningspeed of 200 m/minute at a linear pressure of 40 kgf/cm in a coolingroll and a press roll, to form a lower layer having a thickness of 21 μmand an upper layer having a thickness of 5 μm. The above cooling rollhad a finely roughened surface plated with chromium and was operated ata cooling water temperature of 12° C. Further, the above melt extrusioncoatings of the front surface and the reverse surfaces with the resincompositions were carried out by a so-called tandem method in which theconsecutive extrusion coatings were carried out.

Compounded composition (BL-1): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thefollowing master batch (MB-1W) containing a titanium dioxide pigment, 8parts by weight of pellets of the following master batch (MB-1B)containing a titanium dioxide pigment and Ultramarine and 75 parts byweight of pellets of the following low-density polythylene resin (S1).

Master batch (MB-1W): Master batch prepared by fully kneading 50% byweight of an anatase type titanium dioxide pigment which wassurface-treated with hydrous aluminum oxide (0.50% by weight as an Al₂O₃content based on the titanium dioxide and milled with a steam mill andhad a particle number-average diameter, measured through an electronmicroscope, of 0.120 μm, 47.5% by weight of the following low-densitypolyethylene resin (S-2) and 2.5% by weight of zinc stearate in thepresence of 240 ppm of1,3,5-tris(4-tert-butyl-3-hydroxy-2,4-dimethyl-benzyl)cyanurate as anantioxidant with a Banbury mixer at 150° C., cooling the kneaded mixtureand pelletizing it.

Master batch (MB-1B): Master batch prepared by fully kneading 50% byweight of the same titanium dioxide pigment as the above titaniumdioxide pigment, 46.25% by weight of the following low-densitypolyethylene resin (S-2), 1.25% by weight of Ultramarine and 2.5% byweight of stearin-incorporated zinc in the presence of the sameantioxidant as the above antioxidant with a Banbury mixer at 150° C.,cooling the kneaded mixture and pelletizing it.

Low-density polyethylene resin (S-1): Autoclave-methodhigh-pressure-process low-density polyethylene resin having a density of0.918 g/cm³ and an MFR of 4.0 g/10 minutes.

Low-density polyethylene resin (S-2): Tubular-methodhigh-pressure-process low-density polyethylene resin having a density of0.918 g/cm³ and an MFR of 9.1 g/10 minutes.

Compounded composition (BL-2): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-1W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-1B) containing a titaniumdioxide pigment and Ultramarine, 43.8 parts by weight of pellets of thesame low-density polyethylene resin as the above low-densitypolyethylene resin (S-1) and 31.2 parts by weight of the followinghigh-density polyethylene resin (S-3).

High-density polyethylene resin (S-3): Ziegler-method high-densitypolyethylene resin having a density of 0.967 g/cm³ and an MFR of 6.8g/10 minutes.

Compounded composition (BL-3): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-1W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-1B) containing a titaniumdioxide pigment and Ultramarine, 31.6 parts by weight of pellets of thesame low-density polyethylene resin as the above low-densitypolyethylene resin (S-1) and 43.4 parts by weight of pellets of the samehigh-density polyethylene resin as the above high-density polyethyleneresin (S-3).

Compounded composition (BL-4): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-1W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-1B) containing a titaniumdioxide pigment and Ultramarine, 22.9 parts by weight of pellets of thesame low-density polyethylene resin as the above low-densitypolyethylene resin (S-1) and 52.1 parts by weight of pellets of the samehigh-density polyethylene resin as the above high-density polyethyleneresin (S-3).

Compounded composition (BL-5): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-1W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-1B) containing a titaniumdioxide pigment and Ultramarine, 14.3 parts by weight of pellets of thesame low-density polyethylene resin as the above low-densitypolyethylene resin (S-1) and 60.7 parts by weight of pellets of the samehigh-density polyethylene resin as the above high-density polyethyleneresin (S-3).

Further, after the front and reverse resin sheets were formed and beforethe resin-coated paper was taken up, the reverse resin sheet of theresin-coated paper was subjected to corona discharge treatment, and thenthe following back layer coating liquid was applied on machine. That is,a back layer coating liquid containing colloidal silica:styrene-basedlatex=1:1 and further containing sodium polystyrenesulfonate and aproper amount of a coating aid was applied so as to form a back layerhaving a sodium polystyrenesulfonate content of 0.021 g/m² as a dryweight and a latex content (as a solid content) of 0.21 g/cm² as a dryweight.

After the back layer was formed and before the resin-coated paper wastaken up, the front resin sheet of the resin-coated paper was subjectedto corona discharge treatment, an undercoating liquid containing 1.2 gof lime-treated gelatin, 0.3 g of low-molecular-weight gelatin (P-3226,supplied by Nitta Gelatin K.K.), 0.3 g of a methanol solution containing10% by weight of butyl p-hydroxybenzoic acid and 0.45 g of amethanol/water mixture containing 5% by weight of 2-ethylhexylsulfosuccinate, the total amount of the undercoating liquid beingadjusted to 100 g by adding water, was uniformly applied on machine toform an undercoat layer having a gelatin application amount of 0.06g/m², whereby a support for an imaging material was obtained.

The above-obtained support for an imaging material was evaluated forperformances by the following methods.

A blue-sensitive emulsion layer containing a yellow color formingcoupler was formed on the undercoat layer of the support, and anintermediate layer containing a color mixing preventer, agreen-sensitive emulsion layer containing a magenta color formingcoupler, an ultraviolet absorbent layer containing an ultravioletabsorbent, a red-sensitive emulsion layer containing a cyan colorforming coupler and a protective layer were consecutively formed, with amulti-layer application E bar, to obtain a color printing paper having atotal gelatin amount of 7 g/m². Each color-sensitive emulsion layercontained silver chlorobromide in an amount corresponding to 0.6 g/m ofsilver nitrate, gelatin necessary for the formation and dispersion ofsilver halide and the formation of a film, proper amounts of a foggingpreventer, a sensitizing dye, an application aid, a film curing agentand a thickener and a proper amount of a filter dye.

Then, the above-obtained color printing paper was stored at 35° C. underconstant humidity for 5 days, a group picture (photograph of manypeople) was printed, subjected to development treatments such asdevelopment, bleaching, fixing and stabilization, and then dried toobtain a photographic print. Separately, print samples such as aset-solid white print (not exposed) and a set-solid black print (blackcolor formed) were also prepared. A series of treatments for theexposure, the development and the drying were carried out with anautomatic printer and an automatic developing machine. The colorformation and development procedures were carried out in the order ofcolor formation and development (45 seconds)→bleaching and fixing (45seconds)→stabilization (90 seconds)→drying.

The so-obtained photographic prints of the universal photograph, theset-solid white print and the set-solid black print were totallyevaluated for gloss appearance by 10 people as monitors. The ratings ofevaluation of the gloss appearance are as follows (the larger the gradevalue is, the higher the gloss appearance is, and the smaller the gradevalue is, the lower the gloss appearance is).

Grades 10-9: The gloss appearance is remarkbly or considerably high.

Grades 8-6: The gloss appearance is high.

Grades 5-4: The gloss appearance is low to some extent, while thesupport is acceptable in practical use.

Grades 3-1: The gloss appearance is low, and there is a problem inpractical use.

Further, the support for an imaging material was evaluated for curlresistance as follows. A photographic print having a size of 8.2 cm×11.7cm was visually evaluated for a curled state at 20° C. at 40%RH by 10people as monitors, and the curl resistance was determined on the basisof 10 grades. The ratings of evaluation of the curl resistance are asfollows (the larger the grade value is, the higher the curl resistanceis, and the smaller the grade value is, the lower the curl resistanceis).

Grades 10-9: A support is slightly minus-curled (curled with a backlayer inside) or is flat, and the curl resistance is remarkablyexcellent.

Grades 8-7: A support is slightly plus-curled (curled with animage-forming layer inside), while the curl resistance is excellent.

Grades 6-4: A support is plus-curled to such an extent that there is noproblem in practical use.

Grades 3-1: A support is plus-curled extremely and there is a problem inpractical use.

Table 23 shows the results.

TABLE 23 Density Example Fiber length of resin Density (=Ex.), ofnatural in lower of resin Compar- pulp consti- Compounded layerCompounded in upper ative tuting base compo- (g/cm³) compo- layerExample paper (mm) sition for (Note. sition for (g/cm³) (=CEx.)(Note. 1) lower layer 2) upper layer (Note 2) CEx. 34 0.68 BL-1 0.918BL-4 0.947 Ex. 135 0.62 BL-1 0.918 BL-3 0.942 Ex. 136 0.62 BL-1 0.918BL-4 0.947 Ex. 137 0.62 BL-1 0.918 BL-5 0.952 CEx. 35 0.56 BL-1 0.918BL-1 0.918 CEx. 36 0.56 BL-1 0.918 BL-2 0.935 Ex. 138 0.56 BL-1 0.918BL-3 0.942 Ex. 139 0.56 BL-1 0.918 BL-4 0.947 Ex. 140 0.56 BL-1 0.918BL-5 0.952 CEx. 37 0.56 BL-3 0.942 BL-4 0.947 Example or ComparativeGloss appearance of Example photographic print Curl resistanceComparative Example 34 1 10 Example 135 5 10 Example 136 6 10 Example137 7  9 Comparative Example 35 2 10 Comparative Example 36 3 10 Example138 6 10 Example 139 10  10 Example 140 10   9 Comparative Example 3710   3 Note 1: Pulp fiber length (mm) defined in the presentspecification and found by measuring natural pulp which was toconstitute a base paper. Note 2: Calculated density (g/cm³) of totalpolyethylene resin components in a lower resin layer or an upper resinlayer.

The results in Table 23 show the following. The support III for animaging material, in which one surface of a base paper composed mainlyof a natural pulp where an image-forming material is to be formed iscoated with at least two resin layers, i.e., an upper layer (A)containing at least 50% by weight (as a content based on a total contentof resin components contained in the upper layer) of a polyethyleneresin and a lower layer (B) containing a largest amount (amount based ona total amount of resin components contained in the lower layer) of apolyethylene resin (b), the polyethylene resin (a) having a density ofat least 0.940 g/cm³, the polyethylene resin (b) having a density ofless than 0.940 g/cm³, the upper layer (A) having a thickness equivalentto, or smaller than, 50% of a total thickness of the resin layers, thebase paper being composed mainly of a natural pulp having a fiber lengthin the range of 0.45 to 0.65 mm, i.e., the supports for imagingmaterials in Examples 135 to 140 are excellent supports which givephotographic prints having a high gloss appearance and high curlresistance.

Of the supports III for imaging materials, provided by the presentinvention, in view of the effect on improvement in gloss appearance, thesupport having a base paper composed of a natural pulp having a fiberlength of 0.48 to 0.62 mm is preferred, and the support having a basepaper composed of a natural pulp having a fiber length of 0.50 to 0.59mm is more preferred. Further, in view of the effect on improvement inthe gloss appearance of a photographic print, the density of the totalpolyethylene resin components in the upper layer (A) is preferably atleast 0.940 g/cm³, and more preferably at least 0.945 g/cm³, andparticularly preferably at least 0.950 g/cm³.

On the other hand, when the upper layer does not satisfy therequirements of the present invention (Comparative Examples 35 and 36),when the lower layer does not satisfy the requirements of the presentinvention (Comparative Example 37) or when the fiber length of thenatural pulp constituting the base paper does not satisfy therequirement of the present invention, the support for an imagingmaterial has problems in that it fails to give a photographic printhaving a high gloss appearance or has poor curl resistance.

EXAMPLES 141-144

Example 139 was repeated except that the resin composition for the upperlayer was replaced with a compounded composition (BL-1) or one of thefollowing compounded compositions (BL-6) to (BL-8).

Compounded composition (BL-6): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-1W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-1B) containing a titaniumdioxide pigment and Ultramarine and 75 parts by weight of pellets of thefollowing low-density polyethylene resin (S-4).

Low-density polyethylene resin (S-4): autoclave-method low-densitypolyethylene resin having a density of 0.924 g/cm³ and an MFR of 4.0g/10 minutes.

Compounded composition (BL-7): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thefollowing master batch (MB-2W) containing a titanium dioxide pigment, 8parts by weight of pellets of the following master batch (MB-2B)containing a titanium dioxide pigment and Ultramarine and 75 parts byweight of pellets of the following low-density polyethylene resin (S-5).

Master batch (MB-2W): Master batch prepared in the same manner as in thepreparation of master batch (MB-1W) except that the low-densitypolyethylene (S-2) was replaced with the following low-densitypolyethylene resin (S-6).

Master batch (MB-2B): Master batch prepared in the same manner as in thepreparation of master batch (MB-1B) except that the low-densitypolyethylene (S-2) was replaced with the following low-densitypolyethylene resin (S-6).

Low-density polyethylene resin (S-5): Autoclave-methodhigh-pressure-process low-density polyethylene resin having a density of0.925 g/cm³ and an MFR of 4.0 g/10 minutes.

Low-density polyethylene resin (S-6): Autoclave-methodhigh-pressure-process low-density polyethylene resin having a density of0.925 g/cm³ and an MFR of 7.5 g/10 minutes.

Compounded composition (BL-8): Compounded composition prepared by simplyand fully mixing (dry-blending) 17 parts by weight of pellets of thesame master batch as the above master batch (MB-2W) containing atitanium dioxide pigment, 8 parts by weight of pellets of the samemaster batch as the above master batch (MB-2B) containing a titaniumdioxide pigment and Ultramarine, 86.4 parts by weight of pellets of thesame low-density polyethylene resin as the low-density polyethyleneresin (S-5) and 8.6 parts by weight of the same high-densitypolyethylene resin as the high-density polyethylene resin

Table 24 shows the results.

TABLE 24 Density of Gloss Compounded resin in appearance compositionlower layer of photo- for lower (g/cm³) graphic Curl Example layer Note.2 print resistance Example 141 BL-1 0.918 10 10  Example 142 BL-6 0.92310 9 Example 143 BL-7 0.925 10 8 Example 144 BL-8 0.929 10 6 Note 2: thesame as Note 2 to Table 23.

The results in Table 24 show the following. The supports for an imagingmaterial in the present invention (Examples 141 to 144) are excellentsupports which can give photographic prints having a high glossappearance and excellent curl resistance. In view of the curl resistancein particular, the supports in which the density (calculated density) ofthe total polyethylene resin components of the lower layer is 928 g/cm³or lower are more preferred, and the support in which the above densityis 0.921 g/cm³ or lower is particularly preferred.

EXAMPLES 145-148 AND COMPARATIVE EXAMPLE 38

Example 139 was repeated except that the resin composition (BL-1) for alower layer and the resin composition (BL-4) for an upper layer wereextruded by two-layer co-extrusion coating such that the thickness ofthe lower layer and the thickness of the upper layer were as shown inTable 25. Table 25 shows the results.

Thick- Thick- Ratio of Gloss ness of ness of thickness appearance lowerupper of upper of photo- layer layer layer (%) graphic Curl (μm) (μm)(Note 3) print resistance CEx. 38 13 18 58.1 10 3 Ex. 145 17 14 45.2 106 Ex. 146 21 10 32.3 10 8 Ex. 147 24.8 6.2 20.0 10 10  Ex. 148 21 5 16.110 10  Ex. = Example, CEx. = Comparative Example Note 3: The ratio ofthickness of upper layer to the total resin layer thickness on the frontside.

The results in Table 25 show the following. The supports for an imagingmaterial (Examples 145 to 148) in the present invention in which thefront surface of the base paper is coated with at least two resin layersand the thickness of the upper layer is equivalent to, or smaller than,50% of the total thickness of the resin sheet formed of at least twolayers are excellent supports which can give photographic prints havinga high gloss appearance and excellent curl resistance. Further, in viewof the curl resistance, the supports in which the thickness of the upperlayer is equivalent to, or smaller than, 35% of the total thickness ofthe resin sheet formed of at least two layers are preferred, and thesupports in which the thickness of the upper layer is equivalent to, orsmaller than, 20% of the total thickness of the resin sheet formed of atleast two layers are particularly preferred.

Further, the support for an imaging material (Comparative Example 38) inwhich the thickness of the upper layer is greater than 50% of the totalthickness of the resin sheet formed of at least two layers and which isoutside the scope of the present invention is poor in curl resistanceand has a problem in this regard.

EXAMPLES 149-156 AND COMPARATIVE EXAMPLES 39-40

A base paper having a central plane average roughness SRa shown in Table26 was prepared in the same manner as in Example 139 except that thepulp was replaced with a pulp which was beaten to have a fiber lengthshown in Table 26 and that the linear pressure of the machine calenderwas properly adjusted. The so-obtained base paper in each Example had adensity of 1.02 to 1.10 g/cm³. Example 139 was repeated except that thebase paper used in Example 139 was replaced with the above base paper.Table 26 shows the results.

TABLE 26 Fiber length of natural pulp Central Gloss constituting planeappearance base paper average of photo- Curl (mm) roughness graphicresist- Note 1 SRa (μm) print ance stiffness CEx. 39 0.42 1.01 10  8  3Ex. 149 0.45 1.03 10  9  5 Ex. 150 0.48 1.05 10 10  7 Ex. 151 0.50 1.0810 10  8 Ex. 152 0.53 1.13 10 10  9 Ex. 153 0.56 1.20 10 10 10 Ex. 1540.59 1.30 10 10 10 Ex. 155 0.62 1.37  6 10 10 Ex. 156 0.64 1.45  4 10 10CEx. 40 0.68 1.55  1 10 10 Ex. = Example, CEx. = Comparative ExampleNote 1: The same as Note 1 to Table 23.

The support for an imaging material was evaluated for stiffness asfollows. A 13 cm×18 cm color photographic print prepared in the samemanner as in Example 135 was evaluated by 10 people as monitors. Thecolor photographic print was manually held and shaken up and down toevaluate the stiffness on the basis of manual feeling, and the stiffnesswas determined on the basis of 10 stages of grades. The ratings ofevaluation of the stiffness (the greater the number of grade is, thehigher the stiffness is, and the smaller the number of grade is, thelower the stiffness is) are as follows.

Grades 10-9: The stiffness is high.

Grades 8-7: The stiffness is high to some extent.

Grades 6-4: The stiffness is low to some extent, while the support ispractically acceptable.

Grades 3-1: The stiffness is low, and there is a problem in practicaluse.

The results in Table 26 show the following. The supports for an imagingmaterial in the present invention (Examples 149 to 156) are excellentsupports which can give photographic prints having a high glossappearance, excellent curl resistance and high stiffness. In particular,in view of effects on the improvements in the gloss appearance and thestiffness of a photographic print, the support in which the fiber lengthof the natural pulp is 0.48 to 0.62 mm is preferred, the support inwhich the fiber length of the natural pulp is 0.50 to 0.59 mm is morepreferred, and the support in which the fiber length of the natural pulpis 0.53 to 0.59 mm is particularly preferred. Further, concerning thebase paper for use in the present invention, the base paper having acentral plane average roughness of 1.5 μm or less is preferred, the basepaper having a central plane average roughness of 1.4 μm or less is morepreferred, and the base paper having a central plane average roughnessof 1.3 μm or less is particularly preferred.

On the other hand, the supports for an imaging material (ComparativeExamples 39 and 40) outside the scope of the present invention fail togive a photographic print having high stiffness or fail to give aphotographic print having a high gloss appearance, and thus have aproblem.

EXAMPLES 157-159

Example 139 was repeated except that the running speed of the base paperwas changed as shown in Table 27.

EXAMPLE 160

Example 139 was repeated except that the surface of the base paper,which had been subjected to corona discharge treatment, was coated witha lowermost layer, and then coated with an intermediate layer and anuppermost layer (concurrently), at a base paper running speed of 200m/minute by consecutive melt extrusion coating in different stationswith melt extruders at a linear pressure of 40 kgf/cm in a finelyroughened roll and a press roll, in place of forming the front resinsheet in Example 139. In the consecutive melt extrusion coating in thiscase, as a resin composition for the lowermost layer, the compoundedcomposition (BL-1) was melt-extruded at a resin temperature of 315+ C.to form a layer having a thickness of 16 μm, and then, the compoundedcomposition (BL-1) for an intermediate layer and the compoundedcomposition (BL-4) for an uppermost layer were two-layer co-extruded ata resin temperature of 310° C. each to form the intermediate layerhaving a thickness of 9 μm and the uppermost layer having a thickness of5 μm. In the resin layer constitution of this Example, the uppermostlayer works as an upper layer referred to in the present specificationand the intermediate layer and the lowermost layer work as a lower layerreferred to in the present specification.

EXAMPLES 161-162

Example 160 was repeated except that the running speed of the base paperwas changed as shown in Table 27.

Table 27 shows the results obtained in Examples 157 to 162.

TABLE 27 Method of melt extrusion Gloss Running coating for appearancespeed of lowermost layer of base and uppermost photographic Curl paperlayer print resistance Example 157 200 Co-extrusion 10 10 Example 158250 ″  7 10 Example 159 300 ″  5 10 Example 160 200 Consecutive 10 10extrusion Example 161 250 Consecutive 10 10 extrusion Example 162 300Consecutive 10 10 extrusion

The comparison between of the results in Examples 158 and 161 (runningspeed of base paper 250 m/minute each) and the comparison of the resultsin Examples 159 and 162 (running speed of base paper 300 m/each) showthe following. With an increase in the running speed of the base paper(i.e., the production speed of the support for an imaging material),that is, when the running speed of the base paper is at least 250m/minute, particularly, at least 300 m/minute, of the supports of thepresent invention, the support of which the front resin sheet isconstituted to have a multi-layered structure by a consecutive meltextrusion coating method is particularly preferred in view of effects onthe improvements in the gloss appearance of a photographic print.Further, the above support for an imaging material is an excellentsupport which can give an imaging material and a print thereon whichhave a high gloss appearance, and which can be produced at a high speed.

What is claimed is:
 1. A support for an imaging material, comprising a base paper having a multi-layered structure and a resin sheet having a multi-layered structure, comprising at least one film formable polyolefin resin and being coated on at least an image forming side of said base paper, wherein a paper layer adjacent to the resin sheet on the image forming side has a thickness of at least 10 μm and is composed of a broad-leaved tree pulp beaten to an average fiber length of 0.3 to 0.5 mm; at least one paper layer of the base paper excluding the paper layer adjacent to the resin sheet is composed of a pulp having an average fiber length of over 0.5 mm to 0.8 mm; and the pulp comprising all layers of the multi-layered base paper has a freeness of 250 to 360 ml.
 2. The support of claim 1, wherein the paper layer composed of a pulp having an average fiber length of over 0.5 mm has a thickness equivalent to, or greater than, 50% of the thickness of the base paper as a whole.
 3. The support of claim 1, wherein the uppermost layer of the multi-layered resin sheet on the image forming side contains at least one film formable polyolefin resin having a higher density, a higher melting point or both than a polyolefin comprising another layer of the multi-layered resin sheet on the image forming side.
 4. The support of claim 1, wherein the uppermost layer and the lowermost layer on the image forming side of the base paper in the multi-layered sheet of film formable polyolefin resin are formed by a consecutive extrusion coating.
 5. The support of claim 1, wherein the film formable polyolefin resin contains titanium dioxide.
 6. A support for an imaging material, comprising a base paper having a multi-layered structure and a resin sheet having a single-layered structure consisting entirely of a film formable polyolefin resin and being coated on at least an image forming side of said base paper, wherein a paper layer adjacent to said resin sheet on the image forming side has a thickness equivalent to 10 to 40% of a thickness of said base paper and is composed of a broad-leaved pulp beaten to an average fiber length of 0.3 to 0.5 mm, and at least one paper layer of the base paper, excluding the paper layer adjacent to said resin sheet, is composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved tree kraft pulp and has a total thickness equivalent to 60% to 90% of said base paper.
 7. The support of claim 6, wherein said base paper is a two-layer structure.
 8. The support of claim 6, wherein the film formable polyolefin resin contains titanium dioxide. 